SMITHSONIAN CONTRIBUTIONS TO 

BOTANY 

NUMBER 5 

Burrett Nelson RW~ The Woods and Flora 

of the Florida Keys: 

cc Pinnatae” 

SMITHSONIAN INSTITUTION PRESS 

CITY OF WASHINGTON 

1972 
ABSTRACT 

Barrett Nelson Rock. The Woods and Flora of the Florida Keys: “Pinnatae.” Smithsonian Contributions to Botany, number 5, 35 pages, 35 figures, 1972.-The “Pinnatae,” comprising six families of woody plants with pinnately compound leaves, is 

represented on the Florida Keys by at least 16 species. The taxonomic treatment of 

these families at the ordinal level has been inconsistent. The purpose of this study is 

to correlate the data derived from intensive study of the xylem anatomy of these 16 

species with data from the literature concerning these and other members of the 

families involved, so that new insight might be gained concerning the taxonomic 

relationships among these families. 

This study indicates that the members of the Pinnatae are anatomically homogeneous. All members possess simple perforation plates, vessel elements having alternate 

intervascular pitting, fibrous elements with small slitlike simple to vestigially bordered 

pits, and apotracheal and paratracheal axial parenchyma, or both. Secretory structures, such as crystalliferous idioblasts, parenchymatous cells containing “gum,” and 

intercellular canals, are of wide occurrence within the Pinnatae. In addition, many 

species possess septate fibers and axial parenchyma arranged in aggregate patterns, 

with banded arrangements being most frequent. 

There is no anatomical basis for the separation of families into distinct orders in 

my view. The only separation of families within the Pinnatae suggested by a syndrome of several unique characters, in addition to those common to all members, 

is the formation of an Anacardiaceae-Burseraceae complex. The members of the 

Pinnatae belong to a taxon corresponding well with Cronquist’s Sapindales. 

Phylogenetically, the Pinnatae constitutes an advanced taxon, based on xylem 

anatomy. 

(Scientific Article No. A1731, Contribution No. 4506, of the Maryland Agricultural Experiment 

Station, Department of Botany.) 

Oficial publication date is handstamped in a limited number of initial copies and is recorded 

in the Institution’s annual report, Smithsonian Year. 

UNITED STATES GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1972 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 50 cents (paper cover) 

Stock Number 4700-0152 
Barrett Nelson ROC^ The Woods and Flora 

Introduction 

The Anacardiaceae, Burseraceae, Meliaceae, Rutaceae, Sapindaceae, and Simaroubaceae constitute a 

group of plant families comprising nearly 6,000 

species of pantropical distribution. All are characterized by plants with pinnately compound leaves. 

These six families are represented on the Florida 

Keys by at least 15 genera, each has a single species, 

except for Zanthoxylum, which has two species there. 

This investigation is an intensive study of the secondary xylem of these plants (Table 1). According to 

Brizicky (1962b, 1963)) Picramnia pentandra Swartz 

(Simaroubaceae) , Melicoccus bijugatus (Sapindaceae) , Amyris maritima Jacquin, Zanthoxylum coriaceum A. Richard, and four naturalized species of 

Citrus in addition to C. aurantiifolia (Rutaceae) are 

also to be found on the Florida Keys but are not 

included in this study. Of the plants studied, only 

the familial affinity of the genus Suriana has been 

seriously questioned. The assignment of the othzr 

genera to families has been more or less generally 

accepted. Small (1913) placed the genus Dodonaea 

in his monogeneric Dodonaeaceae. My work has 

been undertaken to correlate the data derived from 

the Florida Keys members of these six families with 

data obtained previously by earlier workers, with the 

hope that the information gained, although based 

on a limited number of genera, will give additional 

insight on the taxonomic relationships of these plants. 

The taxonomic usefulness of data derived from 

study of the secondary xylem of dicotyledons, when 

correlated with morphological, cytological, palynoBarrett Nelson Rock, Department of Botany, University of 

Maryland, College Park, Maryland 20742. 

of the Florida Keys: 

66 Pinnatae” 

logical, and other information has been widely acknowledged (Chalk 1944, Heimsch 1942, Keck 1957, 

Stern 1952, Tippo 1946, and others). Comparative 

anatomical studies of the secondary xylem of some 

or all of the genera treated in this investigation 

(Dadswell and Eckersley 1938, Dadswell and Ellis 

1939, Dadswell and Ingle 1948, Hess 1946, Heimsch 

1942, Kribs 1930, Record 1939, 1941, Webber 1936, 

1941) indicate that, on the basis of wood anatomy, 

a close interrelationship exists among the members of 

these six families. Plant taxonomists, using morphological characteristics, have also come to the same 

conclusion. However, arrangement of these families 

into orders, based in large part upon such morphological characteristics, has been inconsistent. 

Earlier systems of classification, notably those of 

Linnaeus (1753), de Candolle (1824-1873), and 

Bentham and Hooker (1862-1883), were not based 

on concepts of genetic relatedness as we know them 

today. As such, the arrangement of the six families 

within these systems is of little interest, other than 

historical. It is not surprising, however, that these 

families were closely grouped by de Candolle and 

Previous numbers in this series appeared in Tropical 

Woods (Yale University, School of Forestry) under the 

running title, “The Woods and Flora of the Florida Keys”: 

“Introduction” by W. L. Stern and G. K. Brizicky, 107:36- 

65, 1957; “Compositae” by S. Carlquist, 109: 1-37, 1958; 

“Goodeniaceae” by W. L. Stern and G. K. Brizicky, 109: 

38-44, 1958; “Passifloraceae” by W. L. Stern and G. K. 

Brizicky, 109345-53, 1958; and “Wood Anatomy and 

Phylogeny of Batidaceae” by J. McLaughlin, 110: 1-15, 

1959. “Capparaceae” by W. L. Stern, G. K. Brizicky, and 

F. N. Tamolang appeared in Contributions from the United 

States National Herbarium, 34(2) : 25-43, 1963. 

These studies were initiated through a National Science 

Foundation grant to William L. Stern in 1955. 

1 
TABLE 1.-Wood specimens of the Florida Keys “Pinnatae” examined 

Collector and Number Lacation and Herbarium Collection 

Catalog Number Voucher bcality Species 

ANACARDIACEAE 

Metopium taxifem (L.) Kmg & Urban Stern & Brizicky 566 

Toxicodendro- radicans (L. ) Kuntze 

BLTRSEPACEAI 

-- Bursera simaruba (L.) Sarg. 

!GLIACW 

Swietenia mahagani Jacq. 

RUTACEAE 

Amyris elernifera L 

citrus aurantiifolia (L. ) Swing1e 

Zsnthaxylum f- (L.) Sarg. 

-- Z. flavum Whl 

SAPINDACEAE 

3ar3~0spem:m hslicacabm I,. 

Cupania glabra Sw. 

-- Dodonaea viscosa (L.) Jacq. 

Fxothea paniculata (Ass. ) Radlk. 

Hypelate irifoliata Sw 

Sapindus sapanaria L. 

SIMeR0UBACEp.E 

Simarouba glaucB DC. 

~- Suriana maritinla L. 

Stern 2643b 

Stern 2633 

Stern & Brizidq 171 

Stern 1466 

Stern 2624 

Sterr. 2616 

Sterr. & Brizicw 477 

Stern 1455 

Stern 2614 

Stern & bizicky 486 

Stern 2653 

Stern & Brizicky 514 

stern zGn5 

sterr., 2eam33, PhiE’S, 

Rock, & Sweitzer 2761, 

Stern 2656 

Stern a: Bzizizky 419 

Stern 1506 

stern 2691 

stern 128 

Stern & Brizicky 298 

Stern 1513 

stern, Beaman, Fhipps, 

Rock, & Sweitzer 2735 

Stern & Brizicky 466 

Stern 1467 

stern 2612 

Stern a: Brizicky 526 

stern 1468 

stem 2681 

Stern & Brizicky 552 

Stern 2659 

Stem Brizicky 462 

Stem 1497 

Stern 2613 

Stern & Brizicky 230 

stern 1481 

stern 2666 

Y 

MARY 

WRY 

Y 

us 

None 

.WY 

Y 

us 

IWY 

Y 

hWRY 

Y 

IrkRY 

MARY 

MARY 

Y 

35 

MARY 

Y 

Y 

US 

MARY 

Y 

us 

WRY 

Y 

US 

.WY 

Y 

VARY 

Y 

US 

m 

Y 

US 

MARY 

Key Largo 

Key Largo 

Key Largo 

Big Pim Key 

Windley’s Key 

Key Largo 

Key Largo 

Key largo 

Key Largo 

Key Largo 

Key Largo 

&ey Largo 

Key Largo 

Key Iaxo 

3ahia Honda Key 

Key largo 

3ig Pir.e Key 

3ig Pke Key 

Big Pine Key 

sig Pine Key 

Big Pine Key 

Big Pine Key 

Big Fire Key 

Key largo 

Windley’s Key 

Key Largo 

Windley’s Key 

Windley’s Key 

Windley’s Key 

Key largo 

Key largo 

Key Largo 

SiR Pine Key 

Key Largo 

Big Pine Key 

Grassy Key 

Big Pim Key 

‘Method of citation of wood specimens fallows that recam.e?.ded by Stern 8nd Chanbers (l%C). 

hod epecimecs, for which no catalog number is stated, refer to fluid-presemed collectiors 9t the 

University of Maryland. 
NUMBER 5 3 

Bentham and Hooker, for the similarity of gross 

morphology is striking. 

Engler (Engler and Diels 1936) divided these 

families into two orders : Geraniales and Sapindales. 

The Rutaceae, Meliaceae, Burseraceae, and Simaroubaceae were placed in the Geraniales; the Anacardiaceae and Sapindaceae were placed in the Sapindales. Assignment of a family to an order was based 

primarily on the orientation of ovule attachment : 

family members with epitropous ovules were placed 

in the Geraniales, while those with apotropous ovules 

were placed in the Sapindales. The most recent revision of Engler’s “Syllabus der Pflanzenfamilien” 

(Melchior 1961) redistributes the members of the 

Geraniales into a revised Geraniales and a newly 

erected Rutales on the basis of histological differentiation and a trend toward zygomorphy in the flowers. 

The new Geraniales and Rutales are still segregated 

from the Sapindales on the basis of ovule attachment. The families concerned with in this study 

which were included in the Geraniales are now 

placed in the Rutales. 

The phylogenetic schemes used by Hutchinson, 

Hallier, and others, de-emphasized the ovular orientation of Engler. Hutchinson (1926) erected three 

orders to account for these families, separating them 

largely on the presence or absence of gland-dotted 

(pellucid dots) leaves (Figure 5). Those families 

often having members with gland-dotted leaves were 

placed in his Rutales (containing the Rutaceae, Simaroubaceae, and Burseraceae) , while those families 

without gland-dotted leaves were placed either in 

the Meliales or Sapindales. The Meliales (containing 

the Meliaceae) is characterized by members having 

a stamina1 tube which is lacking in members of the 

Sapindales (containing the Anacardiaceae and Sapindaceae) . All of these orders are within Hutchinson’s 

arborescent line of evolution. These three orders plus 

the order Juglandales were grouped by Hutchinson 

in the subphylum “Pinnatae.” The Juglandales was 

later dropped from this subphylum (Hutchinson 

1959). Hallier’s earlier treatment (1905) placed all 

six families in his large cohort, Rosales, with the 

note that it would be further subdivided after “. . . more exhaustive examination.” Hallier ( 1912) later 

combined the members of the Anacardiaceae and 

Burseraceae into a single family, the Terebinthaceae, 

which he included in his Rutales, along with Rutaceae, Meliaceae, and Simaroubaceae. The Sapindaceae was placed in his Sapindales. Wettstein (1935) 

included all six families in his Terebinthales. 

A survey of recently proposed phylogenetic systems 

of classification reveals that the treatment of these 

families is still not uniform. Cronquist (1968) assigns 

the six “mutually interrelated” families to his Sapindales, citing Heimsch’s work (1942) as a primary 

reason. Takhtajan (1966) places the Sapindaceae in 

his Sapindales, moving the remainder of the families 

into his Rutales. Both orders are placed in the superorder Rutinae (which also includes his Geraniales 

and Polygalales). Thorne (1968) places all the families in his Rutales, grouping the families into suborders Rutineae (corresponding to Takhtajan’s Rutales) and Sapindineae (containing the Sapindaceae). (Table 2 offers a summary of the taxonomic 

treatment of these six families.) 

Suriana maritima Linnaeus, generally considered 

within the Simaroubaceae, is seen by Gutzwiller 

(1961), Jadin (1901), Record and Hess (1943), 

Small (1911), Thorne (1968), Wilson (1911), and 

others, as constituting a distinct monotypic family, 

the Surianaceae. Cronquist ( 1968) accepts Gutzwiller’s exclusion of Suriana from the Simaroubaceae, 

but chooses to place this genus with Stylobasium in 

his (Cronquist’s) Stylobasiaceae. This family is included in Cronquist’s Sapindales. On the basis of 

wood anatomy, Webber (1936) states that such a 

separation of Suriana from the Simaroubaceae is not 

justified. 

The distribution and habit of each species dealt 

with in this study vary widely and are listed separately. Data concerning number of species, distribution, and habit were obtained primarily from Brizicky 

(1962a, 1962b, 1962c, 1963). The species are listed 

by family. The collection site of each specimen is 

indicated in Table 1. 

ANACARDIACEAE. Metopium is a genus of three 

species, occurring in the West Indies, southern Florida 

and the Florida Keys, British Honduras, Guatemala, 

and southern Mexico. Metopium toxiferum (L.) 

Krug and Urban, a West Indian species, is found in 

the hammocks, pinelands, and coastal dunes in southern Florida and the Florida Keys. It occurs as a large 

tree in the hammocks and as a shrub in the pinelands 

throughout the Florida Keys. 

Toxicodendron is a largely north temperate zone 

genus of approximately 15 species of North American 

and eastern Asiatic distribution. Toxicodendron ra- 
4 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

TABLE 2.--Com~arison of taxonomic treatments 

Order Sapindales 

Stylabasiaceae' 

Sapindaceae 

Furseraceae 

Anacardisceae 

Simaroubaceae 

Rutaceae 

Meliaceae 

hgler (Melchior 19647 

lrder Rutalesb 

Suborder Rutineae 

Rutaceae 

Simaroubaceae 

Eurseracese 

Meliaceae 

kder Sapindales 

Suborder Anacardineae 

hacardiaceae 

Suborder Sapindineae 

Sapindsceae 

Hutchinson (1959) 

,ubphylw,. HcnataeC 

Order. Rutales 

Futaceae 

Simaroubaceae 

Bursereceae 

Order Meliales 

Meliaceae 

Order Sapindales 

Sapindaceae 

Anacardiaceae 

Tskhtajan (1966) 

superorder Rutinae' 

Order Rlteles 

Anacaraiaceae 

Burseraceae 

Sinaroubaceae 

Rutaceae 

Meliaceae 

Order %piridales 

Sapindaceae 

Thorne (1968) 

luperarder. Rutiflarse 

Order Futales 

Suborder. Rutineae 

Rutaceae 

SLmaroubaceae 

surianaceae 

Meliaceae 

3;rseraceae 

hacardiaceae 

Suborder. Sapindineae 

Sapindaceae 

aInc1uaes - 

this most recent revision of Engler's system (Melchior l%k) the older Geraniales has been subdivided 

into a revised Ceraniales and B newly erected Rutales (containing those families listed above in addition to 

others 1. 

'This subphylum previously included the order Juglandales (1926 ). 

'ffeviously the silperorder Einnatae . 

dicans (L.) Kuntze (Figure 1) is widely distributed 

in woods, thickets, fencerows, and swamps throughout most of southern Canada, the United States, 

northern Mexico, and the West Indk2 It occurs 

as a woody vine throughout its range. 

BURSERACEAE. Bursera is a genus of approximately 100 species, distributed throughout tropical 

and subtropical America. Bursera simaruba (L.) 

Sargent (Figures 2, 3) is found in southern Florida 

and the Florida Keys, the West Indies, southern 

Mexico, Central America, and northern South America. It occurs as a large tree, primarily in the hammock forests throughout the Florida Keys. 

Swietenia, a genus of at least three 

species, occurs in southern Florida and the Florida 

Keys, the West Indies, Mexico, Central America, 

Colombia, Venezuela, and the upper Amazonian 

region. Swietenia mahagoni Jacquin (Figure 4) is 

found in the West Indies, southern Florida and the 

Florida Keys. On the Florida Keys it occurs in the 

hammock forests. It is a large tree throughout its 

range. 

Amyris is a genus of approximately 

20 species, occurring in southern Florida (including 

the Florida Keys) and Texas, the West Indies, Central America, and northern South America. Amyris 

MELIACEAE. 

RUTACEAE. 

Toxicodendron is recognized as distinct from Rhus, 

primarily on the basis of Barkley's monograph (1937). 

elemifera Linnaeus is primarily a West Indian species, 

occurring also in southern peninsular Florida and the 

Florida Keys. It ranges in habit from a shrub to a 

small tree (up to 50 feet tall, with trunks up to a 

foot in diameter), and occurs in the hammock 

forests throughout the Keys. 

Citrus is a highly polymorphic genus with an 

uncertain number of species (16 minimum and 

possibly 145 maximum, Brizicky 1962a), native to 

southern and southeastern Asia and Malaysia. Several species are widely cultivated and have escaped 

to all warm regions of the world (Brizicky 1962a). 

Five species are recorded as more or less naturalized 

throughout southern Florida and the Florida Keys. 

Citrus ourantiifolia (L.) Swingle, the lime (the 

single species of Citrus collected), is a tree native 

to the East Indian Archipelago. It occurs on the 

Florida Keys along roadsides and in secondary woods 

(hammock forests). 

Zanthoxylum, a genus of some 215 species, is 

mainly pantropical in distribution (Brizicky 1962a), 

with several species extending into temperate North 

America and eastern Asia.3 Both of the species en- 

'According to Record and Hess (1943), the genus 

Zanthoxylum comprises only 15 species, all of north-temperate distribution, while the genus Fagara comprises approximately 200 pantropical species. Brizicky ( 1962a) considers Fagara as a synonym for the older Zanthoxylum. 
NUMBER 5 5 

countered in this study are considered native to the 

West Indies (Brizicky 1962a). Zanthoxylum fagara 

(L.) Sargent occurs in central and southern Florida, 

including the Florida Keys, southern Texas, the 

West Indies, Mexico, Central America, and South 

America. It occurs as an armed (spined) shrub oi 

small tree throughout its range. Zanthoxylum flavum 

Vahl occurs as an unarmed small tree on the lower 

Florida Keys (specifically Bahia Honda Key State 

Park) and the West Indies. Both species occur in 

hammock forests. 

SAPINDACEAE. Cardiospermum, a genus of approximately 12 species, is primarily of tropical 

American distribution, with one species occurring in 

tropical West Africa and one ill-defined species 

(Cardiospermum halicacabum L.4) of pantropical 

distribution. Cardiospermum halicacabum (Figure 8), 

a woody perennial vine, occurs in the hammock 

forests on the Florida Keys. 

Cupania is a tropical American genus of approximately 45 species and extends from Argentina and 

Peru north to Mexico and into southern Florida, the 

Florida Keys, and the West Indies. Cupania glabra 

Swartz (Figure 9) occurs in the West Indies, the 

Florida Keys, Mexico, and Central America as far 

south as Costa Rica. It is a small tree of the hammock forests, occurring in Watson’s Hammock on 

Big Pine Key. 

Dodonaea is primarily an Australian genus of approximately 60 species. One species occurs in Madagascar, three occur in Hawaii, and one [Dodonaea 

viscosa (L.) Jacquin] is reported as pantropical in 

distribution. Dodonaea viscosa5 occurs as a small tree 

‘ The treatment of the species Cardiospermum halicacabum accepted in this study is as follows: C. halicacabum 

comprises at least three varieties-halicacaburn, microcarpum 

(syn. C. microcarpum H.B.K.), and corindum (syn. C. 

corindum L.; C. keyense Small)-each of which is considered by some authors (Brizicky 1963) as constituting a 

separate pantropical species. All three varieties are reported 

as occurring on the Florida Keys. 

‘Brizicky (1963) refers to the pantropical species as 

Dodonaea viscosa (L.) Jacquin, noting that this species includes D. jamaicensis de Candolle and D. microcarya Small, 

tentatively accepting SherfT’s concept of a single species 

(D. viscosa) having three distinct pantropical varieties. 

Sherff asserts that all of these varieties occur in Florida. 

Brizicky states, however, that inadequate data make “. . . impossible any conclusion regarding the nature and delimitation of infraspecific categories of D. uiFcosa.” Therefore, 

throughout this paper, the Florida Keys Dodonaea is referred to as D. viscosa. 

in the hammock forests and adjacent pinelands of the 

Florida Keys. 

Exothea is a tropical American genus of three species, ranging from the West Indies, southern Florida, 

Mexico and Central America, south to Costa Rica. 

Exothea paniculata (Jussieu) Radlkofer occurs as a 

small tree in the hammock forests and on calcareous 

soils and shell mounds in southern peninsular Florida, 

the Florida Keys, the West Indies, and Guatemala. 

Hypelate, a genus comprising a single species, H. 

trifoliata Swartz, occurs as a shrub or small tree in 

the hammock forests (and rarely the pinelands of 

Big Pine Key) of the Florida Keys and the West 

Indies. 

Sapindus is largely a tropical genus of approximately 13 species, three of which are distributed in 

the Americas, with the remainder found in eastern 

and southeastern Asia, Oceania exclusive of Australia, and Hawaii. At least two of these species are 

extratropical. The primarily tropical American species, S. saponaria Linnaeus (Figures 6, 7), occurs as 

a tree from Argentina, north into Mexico, the West 

Indies, southern Florida, and the Florida Keys. It 

is a member of the hammock forest flora on the 

Florida Keys. 

Simarouba is a widely distributed tropical American genus comprising from six 

to nine species. Sirnarouba glauca DeCandolle (Figure 10) occurs as a tree in southern Florida and the 

Florida Keys, the West Indies, southern Mexico, 

Central America, and part of South America. It is 

an inhabitant of the hammock forests on the Florida 

Keys. 

Suriana is a monotypic genus of pantropical distribution. The single species, S. maritima L. (Figure 

11) is a small to large shrub (occasionally a small 

tree) of the strand vegetation, occurring along seacoasts throughout its range. 

SIMAROUBACEAE. 

Materials and Methods 

Specimens studied in this investigation are listed in 

Table 1. Dried wood specimens were obtained from 

Dr. William L. Stern. Specimens bearing catalog 

numbers of the Record Memorial Collection, Yale 

University School of Forestry (YW)~, and the Na- 

‘ The Samuel James Record Memorial Collection, originally housed at the Yale University School of Forestry, was 

transferred to the U.S. Forest Products Laboratory in Mad- 
6 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

tional Collection of Woods, Smithsonian Institution 

(USw) , were available as prepared slides. In addition, fluid-preserved specimens bearing Stern collection numbers 2612 through 2764 were utilized (see 

Table 1). All wood samples were collected from 

mature stems and are documented with herbarium 

vouchers, with the exception of Bursera sirnaruba 

Sargent, Stern 2624. 

Microscope slides of specimens bearing Yale or 

Smithsonian catalog numbers had been previously 

prepared from unembedded, dried wood samples. 

The fluid-preserved specimens were embedded in 

celloidin prior to sectioning. All slides prepared specifically for this study from fluid-preserved material 

collected by Stern were sectioned on a sliding microtome. All transverse sections were cut at 20p, while 

radial and tangential sections were cut at 15p, 20p, 

and 30p to provide different thicknesses for optimum 

study of all cells and tissues. The sections were 

stained in safranin and Heidenhain’s iron-alum 

haematoxylin, dehydrated and cleared following 

standard microtechnical procedures, and mounted in 

Canada balsam. Exceptionally hard woods were softened prior to sectioning, either in hydrofluoric acid, 

as outlined in Sass (1958), or by boiling in Aerosol 

OT solution in a reflux apparatus (a modification of 

the procedure outlined by Ayensu 1967). 

Macerations were prepared following a variation of 

Jeffrey’s method. The original method, outlined in 

Johansen ( 1940), was modified in the following manner: tertiary butyl alcohol was used as the dehydrant 

and, upon complete dehydration, a small amount of 

stained cellular material was taken directly from the 

tertiary butyl alcohol and placed into a watch crystal 

containing a mixture of xylene and Canada balsam 

of mounting consistency. The mass of cellular material was then spread throughout the mounting medium by gently mixing with a glass rod. A few drops 

of this mixture were then placed on a microscope 

slide and a cover slip added. 

Selection of the diagnostic characters to be included 

in the descriptions of each species was made from 

those suggested by Tippo (1941). Measurements of 

the length of both fibrous elements and vessel eleison, Wisconsin, in December 1969. It is distinguished from 

other wood collections in the Laboratory through the abbreviation SJRw. Original wood collections at the Laboratory 

bear the abbreviation MADw ; the Record Collection formerly carried the abbreviation Yw. 

ments were made from macerated material. Measurements of pore distribution, pore diameter, and end 

wall angle were made from sectioned material. All 

measurements are recorded in microns (p) . Fibrous elements were measured using a Bausch 

and Lomb Tri-Simplex microprojector, except in a 

few cases where, because of cellular breakage, accurate measurement required the higher magnification 

and resolution available only through the use of a 

compound microscope. Vessel element lengths were 

measured with both the microprojector and the 

microscope, the latter was used when the small size 

of the vessel elements prohibited accurate measurement on the projector. The total length (tail to tail) 

of vessel elements was measured, following the suggestions of Chalk and Chattaway (1934, 1935). 

Tangential pore diameters were measured from 

outside wall to outside wall. Only solitary pores were 

measured except in species where, because of the low 

percentage of solitary pores, measurement of the tangential diameters of pores arranged in radial multiples 

was required. Pore distribution was determined from 

transverse sections, while vessel element end wall inclination was measured on tangential sections. 

In measuring the lengths of the fibrous elements 

and vessel elements, pore diameter, and inclination 

of vessel element end walls, a total of 50 random 

measurements of each character was made for each 

species. From these measurements, a range, a most 

frequent range (within which at least 50 percent 

of the measurements made occur; hereafter abbreviated MFR) , and a mean (average) were calculated, 

except for the inclination of end walls, where only 

a mean was calculated. 

Pore distribution was determined by recording the 

total number of solitary pores, radial multiples, and 

pore clusters seen in a given field of view. Ten fields 

were observed, and the total number of pores in 

each distribution type was converted to a percentage 

of the total number for all categories. In members 

of the Rutaceae, pore chains in addition to radial 

multiples are observed. Because of intergrades between chains and multiples, and the difficulty in distinguishing between each type, the pores of either 

type are reported only as radially oriented (Table 

The terminology used in this investigation generally 

follows that suggested by the Committee on Nomenclature, International Association of Wood Anato3). 
NUMBER 5 

55-90 

2C-75 

83-105 

too-163 

7 

2-7 

1-5 

1-3 

3-8 

TABLE 3.-Pore arrangement, diameter, and wall thickness 

65-10c 

45-85 

50-7C 

POFE DISTRIBUTION (percent) 

4-8 

2-12 

2-7 

SFZCIES 

ANACARDIACEAE 

Metopiwn toxiferum 

Taxicodendran radicans 

SWSERACE.45 

-__ Bursera sinaruba 

MELLACEAE 

Swietenia mahagoni 

RLTTACEAI 

Amyris elemifera 

Citms auranriifolia 

Zamhoxylum fasara 

2. flwm 

SAPIhQACEAE 

-- 

Cardiospermum halicacaburr. 

83-125 

75-95 

60-90 

60-85 

45-73 

85-110 

Cupsnia glabra 

Cadonaea viscasa 

Exathea paniculata 

Hypelate trifoliata 

Sapindus saponaria 

-- 

SIMAROUBACEAE 

Simarouba glauca 

-- Suriana maritime. 

4-13 

2-7 

3-7 

2-8 

3-7 

2-5 

Solitary 

67 

80 

70 

68 

53 

70 

55 42 

75 

35 

43 

50 

59 

78 

40 

41 

mltiples Radially 

Oriented Clusters 

D 

Av g 

- 

- 

78 

52 

88 

-36 

53 

78 

63 

58 

3Zd 

-02 

78 

72 

71 

58 

99 

-75 

58 

- 

IETER 

Range 

40-110 

15-110 

45-110 

65-220 

30-55 

30-110 

30-100 

40-85 

20-50 

60-145 

30-105 

50-100 

50-95 

3C-80 

40-150 

85-260 

30-85 

m 1 Rangeo 

’Numbers in parentheses indicate the range of the number of pores Pound in each category. 

balls between pores in .radial multiples and clusters are the thickest. 

CPore distribution reported a8 “radially oriented” because Of difficulty in differentiating between 

radial multiples and chains. Gxly in the case of Amyris elemifera are the majority of the radially 

oriented pores in distinct chains. 

dSmall pores (see description). 

mists, International Glossary of Terms Used in Wood 

Anatomy (1957), hereafter referred to as the IAWA 

Glossary. General terms used in describing relative 

sizes of structures (e.g., intervascular pit sizes and 

fibrous element, cell wall thickness) are those suggested by Record and Chattaway (1939). 

The terms “fibrous elements” and “imperforate 

tracheary elements” are used here interchangeably 

and refer to the prosenchymatous cell types commonly 

referred to as “fibers.” No attempt was made to 

designate such fibrous elements as either fiber-tra- 

‘ In the parlance of “wood technology” and “forest 

products,” “fibers” also include the tracheids of gymnosperms. 

cheids or libriform wood fibers, because of the tenuous 

nature of the pitting encountered in the species 

studied. 

In describing the simple pits commonly found in 

the parenchymatous cell types encountered in the 

woods under study, the term “fenestriform” is used. 

This term, meaning “windowlike,” is used to describe 

any enlarged, oval to rectangular pit. These enlarged 

pits are considerably broader than the intervascular 

pits in the species being described. The fenestriform 

pits most frequently seen in this study are the enlarged simple components of a half-bordered, vessel 

to parenchyma pit-pair. In some species both components of vessel to parenchyma pit-pairs are fenestri- 
8 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

form in nature. Since the simple fenestriform pits are 

generally larger than the bordered pit of a halfbordered pit-pair, a single fenestriform pit will frequently subtend two or more bordered pits, resulting 

in unilaterally compound pitting. 

Because of the ambiguity, awkwardness, and lack 

of precision involved in employing only names to 

categorize vascular rays (Kribs 1935), a description 

of the ray tissue of each species is given. The terms 

“homocellular” and “heterocellular” are used in the 

literal sense. Rays comprising only a single cell type 

(for example, a ray which consists only of procumbent 

cells) are referred to as homocellular. A ray containing two or more cell types, even though one type 

may be of only rare occurrence, is referred to as 

heterocellular. Since varying degrees of the heterocellular type of ray occur in the woods studied, reference to the predominant cell type or types is given 

in each description. 

In the following anatomical descriptions, characters common to all the species studied are included 

in an initial description. The descriptions of the individual species which follow this are arranged according to family. The arrangement of both families 

and the genera within each family is alphabetical. 

Table 3 contains numerical data concerning the pore 

distribution, pore diameters, and vessel wall thickness 

of each species. Table 4 is a summary of pertinent 

anatomical data obtained from each species and is 

included in order to facilitate comparison. 

Anatomical Descriptions 

of the Woods of “Pinnatae” 

Where growth rings are present, the wood in all 

specimens studied is diffuse-porous (Figure 16), with 

the exception of Toxicodendron radicans, which is 

questionably diffuse-porous (Figure 19) . All perforations are simple (Figure 32), with the exception of 

a single multiple perforation observed in Metopium 

toxiferum. 

Intervascular pitting is alternate in all species 

(Figures 30, 31 ) . Scalariform-like intervascular pitting produced by coalescence of adjacent pits and 

unilaterally compound intervascular pitting (Figure 

31) occur to some extent in each species. Fenestriform pits occur in the axial parenchyma and ray 

parenchyma of each species, while in Bursera simaruba, Metopium toxiferum, and Toxicodendron 

radicans both components of vessel to parenchyma 

pit-pairs are commonly fenestriform (Figure 32). 

Unilaterally compound vessel to parenchyma pitting 

occurs in all species. 

The fibrous elements of all species studied have 

oval to slitlike simple or slightly bordered pits predominating on their radial walls (Figures 28, 29). 

The slitlike inner apertures of any given pit-pair may 

be either crossed at angles to one another, or directly 

superposed. Both configurations are frequently observed on a single specimen. Axial parenchyma is 

present in all species. Vascular tracheids and disjunctive paratracheal parenchyma cells are found in 

all species. 

ANACARDIACEAE 

Metopium toxiferum (L.) Krug and Urban: Faint 

growth rings are present. The pores are angular 

to rounded, with vessel element walls varying in 

thickness from 2p to 7p. 

Vessel element length averages 375p, with a range 

of 19Op to 670p and a MFR of 330p to 450p. Perforations are simple, with the single exception of a 

multiple perforation observed in maceration. The 

arrangement of perforations in this instance is such 

that neither the term reticulate nor foraminate is 

accurately descriptive. It should be noted that because of the fenestriform nature of vessel wall pits 

involved in vessel to parenchyma .pitting, description 

of this perforation plate as multiple may not be accurate. The structure seen may actually be a collection of such fenestriform vessel wall pits, arranged 

at the end of the vessel element in such a manner that 

the impression of a multiple perforation is given. 

Vessel element end walls are inclined at an average 

of 44’. In general, the vessels are ligulate. 

Intervascular pitting comprises medium-sized pits 

ranging from 7p to lop in diameter. Pit borders are 

round to somewhat angular; pit apertures are oval 

and included within the borders. 

Both vessel to axial parenchyma pitting and vessel 

to ray parenchyma pitting are fenestriform in nature, 

both members of a vessel to parenchyma pit-pair are 

oval to somewhat angular and simple. 

The imperforate tracheary elements are nonseptate. 

Fibrous elements are gelatinous in nature (Figure 34), 

and, as such, two measurements of wall thickness 

were made. The rigid lignified portion of the sec- 
NUMBER 5 9 

ondary wall is from lp to 3p thick while the combination of rigid and nonrigid secondary walls seldom 

exceeds 6p. As such, the wall thickness (combined) 

ranges from thin to very thick. The average length 

of the fibrous elements is 683p, with a range of 330p 

to 970p and a MFR of 560p to 860p. 

Vascular rays are predominantly bi- and triseriate. 

Some uniseriates are present and a few rays up to 

five cells wide are seen. These may contain horizontal 

intercellular canals. All rays are heterocellular, comprising upright, square, and procumbent cell types. 

The bi- and triseriate rays frequently possess uniseriate wings of from 2 to 4 rows of square and upright 

cells, or both, the remainder of the ray comprising 

procumbent cells. Many of the uniseriate rays appear 

to be composed largely of square and upright cells, 

or both. The uniseriate rays range from 1 to 8 or 

more cells in height, while the bi- and triseriate rays 

are up to 20 cells (400p) or more in height. Starch 

occurs in many of the ray cells. 

The horizontal intercellular canals seen in the rays 

of this species are of infrequent occurrence in Stern 

2643, but rather frequent in Stern @ Brizicky 556. 

The canals are surrounded by an epithelial lining (1 

to 2 cells thick) composed of small, square to angular 

cells with thin isotropic (optically inactive) cell 

walls. The cells external to the epithelial lining are 

of similar shape and size, but with somewhat thicker, 

optically anisotropic cell walls. These cells tend to 

intergrade with the larger, typical procumbent cells. 

The canals seen in Stern 2643 are apparently at an 

early stage of development, possessing small intercellular spaces or canals, while those seen in Stern 

@ Brizicky 556 are of a later stage of development, 

having massive intercellular spaces or canals. Many 

of these older canals lack any organized epithelial 

layer (apparently due to lysigeny). In the latter 

specimen, the canals are often nearly as wide as the 

ray in which they occur. In both specimens a dense, 

rather darkly staining substance is found in many of 

the canals, in addition to remnants of epithelial cell 

walls. It is apparent that these canals are secretory 

in nature. 

Axial parenchyma is present in both apotracheal 

and paratracheal arrangements. Apotracheal parenchyma forms irregularly spaced bands which vary in 

width from 1 or 2 cells to 10 or more cells wide. 

Bands are independent of growth rings. Paratracheal 

parenchyma is aliform to confluent, leading to some 

localized banding. All the axial parenchyma cell 

types frequently contain starch grains. Crystalliferous 

strands are absent. 

Thin-walled tyloses are seen extending into the 

vessels from both axial and ray parenchyma (Figure 

34). In longitudinal section, a high percentage of the 

fenestriform vessel to ray pits are sites of tylosis formation. 

Toxicodendron radicans (L.) Kuntze : The wood 

is diffuse-porous (Figure 19), although the outer 

growth rings tend to be ring-porous ; faint growth rings 

are present. The pores are circular to somewhat 

angular, with walls ranging in thickness from lp to 

5p. Tangential pore diameters range from 15p to 

11Op. A study of macerated material, however, reveals a number of smaller vessel elements, having 

diameters of less than 15p (as measured on macerated 

material). These vessels could not be included in the 

measurements of diameters in transverse section, because they are not readily distinguishable from imperforate tracheary elements. 

Vessel element length averages 250p, with a range 

of 120p to 360p and a MFR of l60p to 300p. Vessel 

element end walls are inclined at an average of 41°. 

The vessel elements are generally ligulate. 

Intervascular pitting comprises small bordered pits 

ranging in size from 4p to 6p in diameter. The pits, 

generally restricted to the ends of the vessel elements 

(pitting on the body of the vessel elements is relatively infrequent, because of the high percentage of 

solitary pores) , possess circular to lenticular apertures 

included within rounded to angular borders. 

Vessel to axial parenchyma pitting comprises halfbordered to simple pit-pairs. The component pits 

of a simple pit-pair, in the vessel element wall and 

the axial parenchyma wall, are both fenestriform in 

nature. Half-bordered pit-pairs are rather infrequent, 

the bordered pit of the vessel element wall generally 

having large lenticular apertures extending to lenticular borders. These bordered pits are generally larger 

than the intervascular bordered pits and intergrade 

with the fenestriform simple vessel element pits. Vessel to ray parenchyma pitting is very infrequent. 

When present, it resembles the vessel to axial parenchyma pitting. 

The imperforate tracheary elements are septate, 

each cell having a single septum. Fiber walls vary 

in thickness from 1p to 5p and range from very thin 

to thick. A study of macerated material reveals that 
10 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

the fibrous elements may have either attenuated or 

truncate end walls. Fibrous elements contain massive amounts of starch. The average length of the 

fibrous elements is 374p, with a range of 230p to 560p 

and a MFR of 300p to 440p. 

Vascular rays are uniseriate and biseriate, although 

in some cases, a portion of a biseriate ray may be up 

to three cells wide. Square and upright cell types 

occur most frequently, while the procumbent cell 

type is rare. The cell type found in any given horizontal row is frequently constant, with one row composed 

entirely of upright cells while another is composed 

of square cells. The occurrence of two cell types 

within the same horizontal row is relatively infrequent. Arrangement of cell types does not follow a 

pattern. The uniseriate rays vary in height from 2 

cells to 30 cells or more. Approximately 50 percent 

of the ray cells contain a dark-staining substance of 

unknown composition. Ray cells generally contain 

large amounts of starch. 

Axial parenchyma is present in both apotracheal 

and paratracheal arrangement. Diffuse parenchyma 

apparently comprises noncrystalliferous strands. Since 

the fibrous elements of this species are living (septate 

and store starch), it was difficult to determine whether cells, seen in either transverse or longitudinal section, were axial parenchyma cells or fibers. Since 

the other parenchymatous cells (paratracheal parenchyma and ray parenchyma) frequently contained a 

dark-staining substance, this character was used as 

the distinguishing criterion ; cells containing the darkstained substance, when viewed in transverse section, 

were interpreted as diffuse parenchyma. The paratracheal parenchyma is scanty vasicentric to vasicentric, and, as mentioned previously, frequently contains a dark-staining substance similar to that seen 

in the ray tissue. 

A large number of small, thin-walled tyloses are 

present in many of the vessel elements. The tyloses 

contain the dark-staining substance seen in the paratracheal parenchyma cells. This is to be expected, 

since tyloses are extensions of parenchyma cells into 

the vessel lumen. 

BURSERACEAE 

Bursera simaruba (L.) Sargent: Growth rings are 

absent. The pores are somewhat angular and have 

walls lp to 3p thick. 

Vessel element length averages 531p and ranges 

from 300p to 770p; the MFR is 495p to 700p. Vessel element end walls are inclined at an average of 

48'. The vessels may be either ligulate or eligulate. 

Intervascular pitting comprises medium-sized pits 

ranging from 7p to lop in diameter. The pit apertures are lenticular and included within polygonal 

pit borders. 

Vessel to axial parenchyma pitting is rare because 

of the scarcity of paratracheal parenchyma. Where 

it occurs, it is sporadic and irregular to alternate 

and larger than the intervascular pitting. Vessel to 

ray pitting differs from the above in that it is variable in form, ranging from large, generally rectangular fenestriform pits to small, oval pits (Figure 32). 

Both components of the former type of vessel to ray 

parenchyma pit-pair are fenestriform in nature. Both 

vessel to axial parenchyma pitting and vessel to ray 

parenchyma pitting are half-bordered. 

The imperforate tracheary elements are septate, 

having from 3 to 8 septa per cell, 3 being the most 

common. Fibrous elements in Stern 2624 contain 

massive amounts of starch (Figures 12, 13) ; starch 

grains are also seen in Stern 1466. Wall thickness of 

fibrous elements may be classified as very thin, 2p to 

4p thick. The average length of the fibrous elements 

is 809p, the range 440p to 116Op and the MFR 730p 

to 950p. 

Vascular rays are predominantly multiseriate ; some 

uniseriate and biseriate rays are seen. All rays are 

heterocellular, although some of the uniseriate rays 

appear to be homocellular when seen in tangential 

section. A survey of 10 radial sections, however, did 

not reveal such homocellular rays. This is apparently 

related to the nature of cell arrangement. In radial 

section, there are no horizontal rows consisting of 

only one type of ray cell. Those rows containing 

procumbent cells also contain square and upright 

cells, or both. Tangential sections of the same ray 

taken at different points would appear to be homocellular at one point and heterocellular at the other. The 

height of the uniseriate rays is up to 350p (20 cells). 

These are far less frequent in occurrence than are 

the multiseriate rays. 

Multiseriate rays are up to 500p (30 cells) in height 

and up to loop in width. The body of the multiseriate ray is composed of procumbent cells. These rays 

generally have uniseriate wings, 1 to 3 cells high, 

composed of upright and square cells, or both. The 
NUMBER 5 11 

rows of procumbent ray cells are uniform, as is generally true of the rows of upright and square cells 

of the vertical wings. The upright and square ray 

cells of this ray tissue frequently contain optically 

anisotropic, prismatic crystals and starch grains. 

Horizontal intercellular canals are seen in many 

of the multiseriate rays (Figure 24). These canals 

are circular in cross section (as seen in tangential 

section) and surrounded (lined) with thin-walled 

epithelial cells. The walls of the epithelial cells are 

optically isotropic (optkally inactive when viewed 

under crossed nicols) . 

The arrangement of axial parenchyma is difficult 

to determine, because of the difficulty in distinguishing between axial parenchyma cells and the thinwalled, septate, living fibrous elements. As mentioned 

previously, the fibrous elements store starch and, as 

such, carry on one of the functions of axial parenchyma. Determination of the presence of axial parenchyma was made only through study of macerations. 

Distinction between fibrous elements and axial parenchyma cells in macerated material was based on the 

pitting and on the cell wall configuration: the transverse, truncate, horizontal end walls of the parenchyma cells and the septa of the attenuated fibers. 

The axial parenchyma seen in macerations may be 

classified as scanty vasicentric. Apotracheal parenchyma may also be present but is not distinguishable 

in transverse section. 

MELIACEAE 

Swietenia mahagoni Jacquin : Growth rings are 

present. Pores are rounded to somewhat angular with 

vessel element walls varying in thickness from 3p 

to 8p. 

Vessel element length averages 437p, with a range 

of 200p to 720p and a MFR of 390p to 515p.. Vessel efement end walls are inclined at an average of 

62'. Vessel elements may be either ligulate or eligulate. 

Intervascular pitting comprises minute bordered 

pits ranging in size from 2p to 3p in diameter. Pit 

borders are rounded to angular; pit apertures are 

lenticular to oval and are included within the borders. 

Vessel to axial parenchyma pitting and vessel to 

ray parenchyma pitting are very similar in size, 

shape, and arrangement. Both types of vessel to 

parenchyma pitting are half-bordered. The bordered pits of the vessel wall are arranged in an 

alternate pattern, these pits coinciding in shape and 

size to intervascular pits. The simple pits of the 

parenchyma walls are oval to elongate and often 

fenestriform in nature. 

Imperforate tracheary elements are septate, having 

a wall thickness that varies from 2p to 7p, and ranges 

from thin to thick. Septa are thin and there are 

two per cell. The average length of the fibrous elements is 981p, with a range of 650p to 1250p and a 

MFR of 880p to 1160p. 

The vascular rays are uniseriate to multiseriate, 

with rays infrequently up to five cells wide; 3- and 

4-seriate rays are the most frequent. All rays are 

heterocellular. The infrequent uniseriate rays are 

short, ranging from a single cell to eight or more cells 

in height, and composed almost entirely of square 

and upright cells, or both. Biseriate rays are longer 

than uniseriate rays, ranging from 5 to 15 or more 

cells in height, and composed of the same cell types 

seen in the multiseriate rays. Multiseriate rays range 

in height from 10 cells (250p) to 30 cells (700p) 

or more, the longer rays generally resulting from 

vertical fusion of two rays. Bi- and multiseriate rays 

comprise procumbent, square, and upright cell types. 

The procumbent cell type generally makes up the 

multiseriate portion of a given ray, while the square 

and upright cell types comprise the one- to manycelled uniseriate wings or margins (Figure 22). Many 

ray cells contain an opaque, dark-staining substance 

of unknown composition. Most ray cells contain 

starch. Marginal cells are frequently crystalliferous 

idioblasts. The ray tissue is storied. 

Axial parenchyma occurs in both apotracheal and 

paratracheal arrangement. Apotracheal parenchyma 

is present mainly as marginal bands (initial). Some 

diffuse parenchyma is also present. Both types of 

apotracheal parenchyma cells contain starch; either 

may be crystalliferous, the occurrence of crystalliferous idioblasts is infrequent and random. Crystalliferous strands are not present. The paratracheal 

parenchyma is scanty vasicentric to vasicentric. Both 

types of axial parenchyma cells frequently contain 

the same dark-staining substance reported in the ray 

cells. 

Vessels generally contain this dark-staining opaque 

substance also. The vessel elements tend to be storied 

in addition to the rays. 
12 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

RUTACEAE 

Amyris elemifera Linnaeus: Growth rings are present, but not distinct. Pores are rounded in cross section, and have walls 4p to 8p thick. Chains are the 

predominant, radially oriented, pore group. 

Vessel element length average 250~, with a range 

of 110p to 350p and a MFR of 220p to 330p. Vessel element end walls are inclined at an average of 

55’. The vessel elements are generally ligulate. 

Intervascular pitting comprises minute bordered 

pits ranging from 3p to 4p in diameter. Pit apertures 

are slitlike to oval and included within the circular 

pit borders. Vessel to axial parenchyma pitting is rare, 

owing to the scarcity of paratracheal axial parenchyma; where it occurs, it is alternate. Vessel to ray 

parenchyma pitting is alternate. In both types of vessel to parenchyma pitting, the pit-pairs are halfbordered; the vessel pits are similar in size and shape 

to the intervascular pits described above, and the 

parenchyma pits are fenestriform and simple. 

Imperforate tracheary elements are nonseptate, 

having thick cell walls 3p to 7p in thickness. The 

aveage length of these fibrous elements is 443p, with 

a range of 270,~ to 660p and a MFR of 375p to 5301. 

Vascular rays are uniseriate and homocellular, all 

cells are procumbent. Although the orientation of 

individual ray parenchyma cells is horizontal in all 

cases, cell length varies, and in some instances, some 

cells in a horizontal row are nearly square. However, 

since these “square” cells are not a consistent character, either in their occurrence or their arrangement, 

I feel the designation of “homocellular” is justified. 

Rays average from 3 to 10 cells in height, rarely up 

to 19 cells (200p) high. 

Axial parenchyma is present as diffuse and banded 

apotracheal parenchyma and as scanty paratracheal 

parenchyma. The banded apotracheal parenchyma is 

1 to 3 cells wide and continuous; the diffuse parenchyma is present as crystalliferous strands comprising 2 to 8 cells (as viewed in tangential section). The 

crystalliferous parenchyma cells (idioblasts) are 

much enlarged. No starch grains were seen, because 

of the acid-softening treatment. 

Small thin-walled tyloses are present (Figure 33) . An amorphous material is seen in some vessels, perhaps because of gummosis of the parenchyma cells 

forming the tyloses. 

Citrus aurantiifolia (L.) Swingle: Growth rings 

are present. The pores are circular, with walls ranging from 4p. to 8p thick. Radial multiples are the 

predominant, radially oriented, pore group. 

Vessel element length averages 273p, with a range 

of 150p to 420p and a MFR of 235p to 340p. Vessel element end walls are inclined at an average of 

58’. Vessel elements may be ligulate or eligulate. 

Intervascular pitting consists of small pits, ranging 

from 4p to 6.p in diameter. Pit apertures are rounded 

to oval and included within round to polygonal borders. 

Vessel to axial parenchyma pitting is alternate. 

The pits found in the vessel element walls are similar 

in size to intervascular pits, while those found in the 

axial parenchyma walls are larger and simple. Vessel to ray parenchyma pitting is alternate and resembles the vessel to axial parenchyma pitting. 

Fibrous elements are nonseptate, having thin walls 

from 2p to 5.u thick. The average length of the 

fibrous elements is 752p, with a range from 400p to 

1150p and a MFR of 560p to 890p. 

Vascular rays are uniseriate to triseriate, some rays 

rarely 4 cells wide. The uniseriate rays range from 1 

to 12 cells (150p) in height and are heterocellular. 

The biseriate and triseriate rays are up to 40 cells 

(500p) in height and are heterocellular, a few having uniseriate wings of from 1 to 4 cells high. In 

the case of both uniseriate and multiseriate rays, the 

great majority of cells are procumbent. Very few 

upright cells were seen in the material studied, arrangement of the cell types follows no pattern, and 

although the margins of the multiseriate rays may 

be a mixture of procumbent and square cells, the 

body of the ray comprises only procumbent cells. The 

ray cells in contact with vessel elements are frequently disjunctive. Most ray cells contain starch grains. 

Axial parenchyma is present in both apotracheal 

and paratracheal arrangements. The apotracheal 

parenchyma is banded, diffuse, and diffuse-in-aggregates, some of which comprise crystalliferous 

strands of from 3 to 20 cells. The banded apotracheal 

parenchyma is made up of axially elongate parenchyma strand cells, some of which have further subdivided and are crystalliferous (crystalliferous 

strands). Many of the cells of the diffuse and diffuse-in-aggregates parenchyma are crystalliferous. 

The crystalliferous idioblasts are generally much enlarged, containing optically anisotropic prismatic 
NUMBER 5 13 

crystals (Figure 25). The bands of axial parenchyma 

are from 1 to 4 cells wide and are continuous. Paratracheal parenchyma is scanty vasicentric and sometimes aliform. Axial parenchyma cells are frequently 

disjunctive. Most, if not all, of the axial parenchyma 

cells contain starch. 

The vessels often contain a granular to nongranular, translucent amorphous material aggregated 

on or near the perforation plates. 

Zanthoxylum fagara (L.) Sargent : Faint growth 

rings are present. Pores are circular, with walls ranging in thickness from 2p to 12p. Radial multiples 

are the predominant radially oriented pore group 

(Figure 14). 

Vessel element length averages 261p, with a range 

of 145p to 465p and a MFR of 210p to 310p. Vessel element end walls are inclined at an average of 

64’. Vessel elements may be either ligulate or 

eligulate. 

Intervascular pitting comprises minute bordered 

pits ranging from 2p to 3p in diameter. Pit apertures 

are oval to lenticular and included within rounded 

borders. 

Vessel to axial parenchyma pitting and vessel to 

ray parenchyma pitting are similar in size, shape, 

and arrangement. The pit-pairs are half-bordered, 

with the bordered vessel element pits similar in size, 

shape, and arrangement to the intervascular bordered pits described above. The simple parenchyma 

pits (both axial and ray parenchyma) are generally 

circular to oval and are either approximately the 

same size as the bordered pits or large, elongate, and 

fenestriform. 

The imperforate tracheary elements are nonseptate, 

having walls which range in thickness from 2p to 6p 

and from thin to very thick (lumens entirely occluded). The length of the fibrous elements averages 

735p, with a range of 400p to 11 75p and a MFR of 

600p to 1OOOp. 

Vascular rays are predominantly uniseriate and 

biseriate, with a few triseriate for at least a part of 

their length. All ray types are heterocellular. Uniseriate raps are frequently short, ranging in height from 

2 to 6 cells or more, and are composed of either 

square or upright cells, or both. A second type of 

uniseriate ray is generally higher, ranging up to 10 

cells or more in height, and consists of procumbent 

cells in addition to square and upright celIs, or both. 

The biseriate rays are generally higher than the 

uniseriates, ranging up to 400p (30 cells) or more 

in height, the biseriate portion of the ray is typically 

composed of only procumbent cells, while the uniseriate margins or “wings” are composed of 1 to 5 or 

more horizontal rows of square and upright cells, or 

both. Starch is not present in the ray cells, possibly 

because of the hydrofluoric acid treatment of the 

specimen (Stern 2625) prior to sectioning. 

Axial parenchyma is present in apotracheal and 

paratracheal arrangement. The apotracheal parenchyma occurs as continuous bands, ranging from 2 to 

7 or more cells in width, comprising strand parenchyma. Generally there are two cells per strand, although in some cases, one or both of these cells has 

further subdivided several times, giving rise to short 

strands of crystalliferous idioblasts. Scanty diffuse 

parenchyma comprises the same cell type as described 

above. The paratracheal parenchyma is scanty vasicentric. 

Irregular and continuous periclinal cavities occur 

throughout the xylem of Stern 2625 (Figures 26, 27). 

These cavities are apparently traumatic in origin and 

contain an evenly staining, homogeneous, opaque to 

transparent substance. Many of the vessels contain 

a granular to nongranular (similar in appearance to 

the homogeneous material seen in the traumatic 

cavities described above) , translucent to transparent 

material. 

Zanthoxylum flavum Vahl: Growth rings are 

present. Pores are circular to somewhat angular, with 

the vessel element walls ranging in thickness from 2p 

to 7p. The bulk of the radially oriented pores are 

intergrades between radial multiples and chains in 

which at least some pores have flattened tangential 

walls. 

Vessel element length averages 575p, with a range 

of 300p to 750p and a MFR of 475p to 650p. Vessel element end walls are inclined at an average of 

44’. The vessel elements are generally ligulate. 

Intervascular pitting comprises small bordered pits 

ranging in size from 4p to 6p in diameter. The pit 

apertures are oval to lenticular and are included 

within rounded to somewhat angular borders. 

Vessel to axial parenchyma pitting and vessel to 

ray parenchyma pitting is similar in size, shape, and 

arrangement. The pit-pairs are half-bordered and 

alternately arranged. The bordered pit of the vessel 

element wall coincides in size and shape with those of 

the intervascular pit-pairs. Simple pits of the paren- 
14 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

chyma wall are round to oval and frequently elongate, the latter fenestriform. 

The imperforate tracheary elements are nonseptate. 

having walls that vary in thickness from 2p to 5p 

and range from thin in early wood to thick and very 

thick in late wood. These walls are optically inactive 

and, as such, may indicate that the fibers are actually 

gelatinous. The average length of the fibrous elements is 1125p, with a range of 735p to 1428~ and 

a MFR of 945p to 1300p. 

Vascular rays are uniseriate to triseriate, with 

biseriate rays predominating. The uniseriate rays 

range from 1 to 7 or more cells high and most 

frequently comprise only square and upright cells, 

or both. Some procumbent cells are seen in the 

uniseriate rays. Bi- and triseriate rays are approximately the same size, ranging from 5 cells to over 

25 cells (600p) in height. In both the bi- and triseriate rays, the multiseriate portion of the ray comprises procumbent cells, while the uniseriate “wings” 

or margins frequently comprise only square and upright cells or both. The rays are heterocellular, comprising all three cell types. Ray cells contain massive 

amounts of starch and are frequently crystalliferous. 

Axial parenchyma is present in apotracheal and 

paratracheal arrangements. The apotracheal parenchyma occurs as continuous bands, which are 

usually, but not necessarily, marginal. When clearly 

marginal, these bands are initial and are 1 to 2 cells 

in width. The bands comprise strand parenchyma, 

many of which, having further subdivided, contain 

nonenlarged, optically active crystals. Diffusely arranged crystalliferous strands are infrequently seen. 

The paratracheal parenchyma is exceedingly scanty, 

not common to every vessel, and never completely 

vasicentric. All types of axial parenchyma contain 

massive amounts of starch. 

SAPINDACEAE 

Cardiospermum halicacabum L. : Faint growth rings 

are present. Pores are rounded to somewhat angular 

with walls varying in thickness from 4p to lop thick. 

Two distinct sizes of vessel elements are present in 

this species (Figure 35.) The smaller of the two 

sizes is generally angular and arranged in radial 

multiples. These vessel elements are ligulate and 

have end walls inclined at an average of 45’ (the 

measurement of the end wall angles are made on 

macerated material) . These small vessel elements 

intergrade with vascular tracheids. 

The larger of the two sizes are rounded and are 

either solitary or arranged in clusters. The large 

vessel elements are either ligulate or eligulate, with 

nearly horizontal end walls. 

The average end all inclination of the combined 

vessel element types, as measured in tangential section, is 76’. The average vessel element length is 

200p, with a range of 130p to 290p and a MFR of 

Intervascular pitting comprises small pits, ranging in size from 4p to 6p in diameter. Pit apertures 

are oval to lenticular. Pit borders are rounded. 

Vessel to axial parenchyma pitting and vessel to 

ray parenchyma pitting, when viewed in section, are 

similar in appearance. The pit-pairs in both types 

of pitting are half-bordered. Pits in the vessel element wall are similar in size, shape, and arrangement to intervascular pits. A study of macerations 

reveals that the simple pits of the ray parenchyma 

are frequently small and slitlike to oval, while those 

of the axial parenchyma are large, oval to elongate, 

and fenestriform. 

Imperforate tracheary elements are frequently 

septate, having walls from 2p to 4p thick, ranging 

from very thin to thick. The average fibrous element 

length is 533p, with a range of 350p to 800p and a 

MFR of 440p to 60011.. 

A study of macerations indicates that two distinct 

types of fibrous elements are present. One type is 

typically thick-walled, having attenuated ends and 

infrequent, thin, solitary septa. The second type of 

fibrous element is generally thin-walled, having 

truncate end walls. This second type is frequently 

septate. Septa are thick and range from 1 to 3 or 

more per cell. Pitting is similar in both types and 

each may contain starch. 

Vascular rays are uniseriate to multiseriate, some 

rays are 4 or more cells wide. The multiseriate rays 

frequently have uniseriate margins. The rays range 

in height from a few cells to over 40 cells (800p). 

The ray tissue is heterocellular, comprising upright, 

square, and procumbent cell types. Upright and 

square cells are most frequent, while procumbent 

cells are relatively rare. The arrangement of cell 

types follows no discernible pattern. Two or more 

cell types are commonly found in any given horizontal row. Ray cells are often crystalliferous or 

160p to 250p. 
NUMBER 5 15 

contain starch. Some of the ray cells contain a darkstaining, transparent to opaque substance of unknown composition. 

Axial parenchyma is present in both apotracheal 

and paratracheal arrangement. Diffuse parenchyma 

usually comprises crystalliferous strands. Additional 

apotracheal parenchyma is present in the form of a 

discontinuous band that may have been traumatic 

in origin in my specimen. Cells in these apotracheal 

parenchyma bands are also frequently crystalliferous. 

The crystalliferous idioblasts are nonenlarged rectangular cells, each containing a single optically 

anisotropic prismatic crystal. They are arranged in 

short vertical strands of from 3 to 10 or more cells. 

The paratracheal parenchyma is generally scanty 

vasicentric, although a few cases of vasicentric are 

seen. Axial parenchyma cells are frequently disjunctive. Both types of axial parenchyma contain massive 

amounts of starch and may contain the dark-staining 

substance seen in ray cells. 

Cupania glabra Swartz: Growth rings are present 

but not distinct. The pores are rounded, having walls 

from 2p to 7p thick. 

Average vessel element length is 414p, with a 

range from 65p to 610p and a MFR from 

340p to 500p. Vessel element end walls are inclined 

at an average of 44'. The vessel elements are generally ligulate. 

Intervascular pitting comprises minute bordered 

pits which range from 2p to 4p in diameter. Pit 

borders are rounded; pit apertures are rounded to 

elliptical and are included within the borders. 

Vessel to axial parenchyma pitting is alternate to 

scattered. Many of the pits in the parenchyma cell 

walls are large, simple, and fenestriform with irregularly shaped margins. The pits in the vessel walls 

are slightly to completely bordered. Vessel to ray 

parenchyma pitting is the same as that described for 

vessel to axial parenchyma pitting. 

The imperforate tracheary elements are septate. 

Most of the fibrous elements contain 2 or more 

septa. The cell walls are 2p to 5p thick and are thin 

as compared with the diameter of the lumen. The 

average length of the fibrous elements is 697p, with 

a range of 375p to 950p and a MFR of 630p to 

840p. 

Vascular rays are, for all intents and purposes, 

uniseriate. A few rays possess biseriate segments but 

these are localized and never extend the length of a 

ray. The rays may be up to 20 cells (300p) or more 

in height, but generally range from 4 to 10 cells 

high. Rays are heterocellular, comprising mainly 

procumbent and square cells, with upright cells occurring infrequently. There is no pattern of arrangement of cell types, although the procumbent cell 

type makes up the bulk of most rays, while the square 

cell type frequently occurs in marginal rows. Both 

square and procumbent cells occur in the same horizontal row. Most of the ray cells contain a darkstaining, transparent to opaque substance of unknown 

composition. 

Axial parenchyma is present in both apotracheal 

and paratracheal arrangements. Apotracheal parenchyma is mainly diffusely arranged, crystalliferous 

strand parenchyma. There is continuously banded 

apotracheal parenchyma 1 to 3 cells wide. The 

diffuse crystalliferous strands are of frequent 

occurrence, and range up to 30 cells or more 

in height. Strand cells, when viewed in longitudinal 

section, are rectangular, with most of the cells in a 

given strand being crystalliferous. Apotracheal bands 

comprise primarily crystalliferous strand parenchyma, 

but unlike the diffuse strands, the cells of the bands 

contain the same dark-staining substance seen in the 

ray cells. The paratracheal parenchyma is scanty 

vasicentric and frequently contains the same darkstaining substance previously mentioned, 

Dodonaea viscosa (L.) Jacquin: Growth rings are 

absent. Pores are circular with walls varying in 

thickness from 3p to 7p. 

Vessel element length averages 234p, with a range 

of 120p to 330p and a MFR of 200p to 270p. Vessel 

element end walls are inclined at an average of 54'. 

Vessel elements are either ligulate or eligulate. 

Intervascular pitting comprises minute bordered 

pits ranging from 2p to 4p in diameter. Pit borders 

are rounded; pit apertures are lenticular and slightly 

extended beyond or included within the borders. 

Vessel to axial parenchyma pitting and vessel to 

ray parenchyma pitting are very similar and both 

fit the following description. The arrangement of 

pits in the vessel wall is alternate. Vessel to parenchyma (both types) pit-pairs are half-bordered; the 

bordered pit of the vessel wall coincides in size and 

shape to the intervascular pits, while the simple pits 

of the parenchyma wall are generally irregularly 

shaped, ranging from circular to elongate, and are 

frequently fenestriform. 
16 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

Imperforate tracheary elements are nonseptate, 

having a wall thickness from 3p to 7p which ranges 

from thick to very thick, the lumens of some cells 

entirely occluded. The average length of the fibrous 

elements is 525p, with a range of 250p to 720,~ and a 

MFR of 440p to 650p. 

Vascular rays are predominantly uniseriate. Some 

biseriates are present, either as short biseriate segments in otherwise uniseriate rays or as completely 

biseriate rays. The rays are heterocellular, comprising 

procumbent and square cells. Very few upright cells 

are seen. There is no discernible pattern of cell arrangement and both square and procumbent cell 

types frequently occur in the same horizontal row. 

There is a tendency, however, for the main body of 

a given ray to be composed primarily of procumbent 

cells. The occurrence of the square cells is sporadic 

in all cases, their arrangement random. 

Uniseriate rays range in height from 2 to 20 cells 

(300p) or more, while the biseriates generally range 

from 5 to 15 cells in height. The ray cells frequently 

contain a dark-staining, transparent to opaque substance of unknown composition. 

Axial parenchyma is present in both apotracheal 

and paratracheal arrangement. Apotracheal parenchyma is primarily diffuse, consisting mainly of 

crystalliferous strands. Some continuously banded 

parenchyma occurs, these bands ranging in width 

from 1 to 3 or more cells. The diffuse crystalliferous 

strands are generally short, usually 10 or fewer cells 

per strand, and composed of slightly enlarged idioblasts, each containing a single optically anisotropic 

prismatic crystal. The paratracheal parenchyma 

ranges from scanty vasicentric to aliform, with infrequent confluent banding occurring. This banding 

is local (not continuous) and is definitely associated 

with the vessel elements. Axial parenchyma frequently contains the dark-staining material seen in 

the ray cells. 

Exothea paniculata (Jussieu) Radlkofer: Growth 

rings are present. Pores are rounded; the walls are 

from 2p to 8p thick. 

Vessel element length averages 428p, and ranges 

from 245p to 560p, with a.MFR of 400p to 500p. 

Vessel element end walls are inclined at an average 

of 43 O, Vessel elements are generally ligulate. 

Intervascular pitting comprises minute bordered 

pits, ranging from 2p to 3p in diameter. Pit borders 

are circular; pit apertures are lenticular and extend 

beyond the pit borders. 

Vessel to ray parenchyma pitting and vessel to 

axial parenchyma pitting are very similar in appearance. In both cases, the arrangement of pits in the 

vessel wall is alternate and the pits are similar in 

size and shape to intervascular pits. The vessel to 

parenchyma pit-pairs (both types of parenchyma) 

are half-bordered, with the simple pits of the parenchyma wall ranging from circular to elongate, and 

fenestriform. 

The imperforate tracheary elements are septate, 

most having two or more septa per cell. The cell 

walls are 2p to 5, thick, and range from thin in 

early wood to very thick in late wood. The average 

length of the fibrous elements is 716p, and the range 

is 440p to 1010p with a MFR of 630p to 800p. The 

fibrous elements often contain starch. 

Vascular rays are uniseriate and biseriate, the 

latter type predominating. Uniseriate rays are generally low, most are from 2 to 5 cells high. The biseriate rays are somewhat higher, generally ranging 

from 8 to 15 cells (250p). Upright cells are rare. Arrangement of these cell types follows no pattern; 

both procumbent and square cells occur in the same 

horizontal rows. Procumbent cells predominate and 

comprise the bulk of most rays. Most ray cells contain a dark-staining, transparent to opaque substance of unknown composition in addition to starch. 

Axial parenchyma is present in both apotracheal 

and paratracheal arrangement. Apotracheal parenchyma is present in diffuse crystalliferous strands and 

as banded and marginal parenchyma. The crystalliferous strands are of frequent occurrence and range 

up to 20 cells or more in height. Crystalliferous idioblasts do not appear to be enlarged and each generally contains a single prismatic crystal. Bands of 

parenchyma may be up to 5 cells wide and are composed of both crystalliferous and noncrystalliferous 

strands. The bands may or may not be marginal and 

are unevenly spaced. The arrangement of the paratracheal parenchyma ranges from scanty vasicentric 

to vasicentric. 

All types of axial parenchyma cells frequently contain starch and the dark-staining substance seen in 

the ray cells. This dark-staining substance may also 

occur in the vessels. 

Hypelate trifoliata Swartz: Faint growth rings are 

present. Pores are rounded, with walls varying in 

thickness from 3p to 7p. 
NUMBER 5 17 

Vessel element length averages 319p, with a range 

of 200p to 515p and a MFR of 275p to 400p. Vessel 

element end walls are inclined at an average of 47'. 

The vessel elements are generally ligulate. 

Intervascular pitting comprises minute pits ranging from 2p to 4p in diameter. Pit apertures are 

rounded to oval and included within rounded to 

polygonal borders. 

Vessel to axial parenchyma pitting and vessel to 

ray parenchyma pitting are similar in appearance. 

Both are alternate to scattered in arrangement and 

half-bordered, the pits in the vessel walls are similar 

in size and shape to the intervascular pits. 

The imperforate tracheary elements are nonseptate, having walls which vary in thickness from 

3p to 7p and range from thick to very thick, the 

lumens of some cells entirely occluded. The average 

length of the fibrous elements is 632p, with a range 

of 420p to 850p and a MFR of 525p to 780p. 

Vascular rays are uniseriate. The rays are heterocellular, comprising procumbent, square, and upright cells. The main body of most rays is composed 

of square and procumbent cells, both frequently occurring in the same horizontal row. Upright cells 

are generally found in the marginal rows. The rays 

range in height from 2 to 25 cells (350p) or more, 

most rays are 10 or fewer cells high. 

Axial parenchyma is present in both apotracheal 

and paratracheal arrangement. Apotracheal parenchyma is diffuse and comprises crystalliferous and 

noncrystalliferous strands. The crystalliferous strands 

range from 4 to 30 cells or more per strand, comprising square idioblasts, each containing a single 

prismatic crystal. Paratracheal parenchyma ranges 

from vasicentric to aliform, with some confluent 

present. A few of the paratracheal parenchyma 

strands contain crystalliferous cells. 

Sapindus saponaria Linneaus : Growth rings are 

absent. The pores are circular and have walls from 

2p to 5p thick. 

Vessel element length averages 278p, with a range 

of 120p to 390p and a MFR of 220p to 330p. End 

walls are inclined at an average angle of 62'. In 

general, the vessel elements are ligulate. 

Intervascular pitting consists of minute pits, ranging from 3p to 4p in diameter. The pit apertures are 

oval to lenticular and included within rounded to 

somewhat angular borders. 

Vessel to both axial and ray parenchyma pitting 

is alternate and half-bordered in nature. The 

bordered to slightly bordered pits in the vessel walls 

are very similar in size and shape to intervascular 

pits, while the pits in the parenchyma walls are 

large and simple. 

Imperforate tracheary elements are septate, generally having a single thin septum in each cell. Walls 

vary in thickness from 2p to 4p and are thin in comparison with the dimensions of the lumens. The average length of fibrous elements is 911p, with a range 

of 650p to 1180p and a MFR of 800p to 1100p. 

Vascular rays are uni- to triseriate, with biseriate 

and triseriate rays predominating. Rays are homocellular, comprising only procumbent cells. The uniseriate rays are generally short, from 2 to 10 or more 

cells high. A few of the uniseriate rays, when seen in 

tangential section, appear to be made up of some 

enlarged square type cells. However, examination of 

radial sections showed that, although some cells were 

higher than other cells, they were nevertheless radially elongate and thus procumbent. The biseriate 

and triseriate rays are generally higher than the uniseriates, ranging up to 50 cells (400p) or more in 

height. Infrequently, enlarged marginal cells are in 

the bi- and triseriate rays, but examination of radial 

sections shows that these cells, although somewhat 

larger, are still radially elongate. All of the rays frequently contain large amounts of starch (starch 

grains). 

Axial parenchyma is abundant and confluent. 

Whether this situation represents true confluent, that 

is, paratracheal, parenchyma is difficult to determine, 

for the bands of axial parenchyma are frequently so 

wide as to occupy a large proportion of the groundmass (Figure 18). These numerous, wide bands thus 

surround most of the vessels (pores). It would be 

impossible, without ontogenic studies, to say whether 

this is fortuitous. The bands comprise two types of 

strand parenchyma: strands of 2 to 4 axially elongate 

cells, and strands of many cells, a large number of 

these crystalliferous. The largely crystalliferous strand 

parenchyma is commonly found at the margins of 

the parenchyma bands. These strands were not seen 

distributed among the fibrous elements. The crystalliferous idioblasts are not enlarged. Distinctly vasicentric parenchyma is also seen in which cells are 

typically flattened and frequently disjunctive, forming a complete sheath around each vessel or group of 

vessels. These cells are distinct from the remainder 
18 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

of the axial parenchyma because they contain the 

same darkly stained substance found in the vessels. 

Starch grains often occur in cells of the banded 

parenchyma, but not in cells of vasicentric parenchyma. 

SIMAROUBACEAE 

Simarouba glauca DeCandolle : Growth rings are 

absent. Pores are circular, with walls from 3p to 12p 

thick. 

Vessel element length averages 446p, with a range 

of 270p to 560p and a MFR of 400p to 500p. Vessel 

element end walls are inclined at an average of 60’. 

Vessel elements are generally eligulate. 

Intervascular pitting comprises small bordered 

pits, ranging in size from 5p to 7p in diameter. Pit 

apertures are oval and included within rounded to 

somewhat angular borders. 

Vessel to axial parenchyma pitting and vessel to 

ray parenchyma pitting is similar in size, shape, and 

arrangement. The pit-pairs are half-bordered, the 

bordered pits of the vessel wall alternate and similar 

in size to the intervascular pits. The simple pits of 

the parenchyma are round to elongate, frequently 

fenestriform. 

Imperforate tracheary elements are nonseptate, 

having walls which range in thickness from 1p to 3p 

and vary from thin to very thin. The average length 

of the fibrous elements is 794p, with a range of 550p 

to 111Op and a MFR of 650p to 950p. 

Vascular rays are uniseriate to multiseriate, with 

biseriate and triseriate rays predominating. Infrequently, the rays are up to five cells wide. All of the 

rays are similar in size, although the uniseriates are 

generally shorter than the bi- and triseriates. The 

uniseriate rays range from 4 to 10 cells or more high. 

The bi- and triseriate rays range from 5 to 30 cells 

(400p) or more high. Rays are heterocellular, although composed almost entirely of procumbent 

cells: square cells are seen, but are infrequent in 

occurrence and random in arrangement. The rays 

cells frequently contain starch. Rays are storied 

(Figure 23). 

Axial parenchyma is present in paratracheal arrangement as narrow, anastomosing confluent bands. 

The bands are frequently continuous and range from 

3 to 10 cells or more wide. Some of the bands are 

discontinuous and, as such, constitute an aliform configuration with long “wings.” Axial parenchyma comprises strands generally consisting of four cells each. 

The strands tend to be storied. (Figure 23). Crystalliferous strand parenchyma is also present, each 

strand consisting of 5 to 10 or more cells. The 

crystalliferous idioblasts are rectangular, nonenlarged 

cells, each containing a single optically anisotropic 

prismatic crystal. Axial parenchyma cells that are in 

contact with vessel elements are generally flattened 

and frequently disjunctive. Cells in strand parenchyma frequently contain starch. 

Suriana maritima Linnaeus: Growth rings are absent. Pores are circular, with vessel element walls 

ranging in thickness from 2p to 6p. 

Vessel element length averages 173p, with a range 

of 45p to 230p and a MFR of 165p to 200p. Vessel 

elements are generally eligulate. 

Intervascular pitting comprises minute bordered 

pits ranging in size from 3p to 4p in diameter. Pit 

apertures are lenticular to oval and are included 

within or are extended slightly beyond the rounded 

to somewhat angular borders. 

Vessel to axial parenchyma pitting and vessel to 

ray parenchyma pitting are similar in size, shape, and 

arrangement. The pit-pairs are half-bordered and 

alternately arranged. The bordered pits of the vessel 

elements are similar to intervascular pits, while the 

simple pits of the parenchyma (both ray and 

axial) are frequently large, oval to elongate, and 

fenestriform. 

Imperforate tracheary elements are nonseptate, 

having walls which vary in thickness from 2p to 6p 

and range from thin to thick. Some of the fibrous 

elements in Stern @ Briticky 230 are gelatinous and 

in Stern @ Brizicky 230 and Stern 2666 they contain 

a darkly staining, translucent to opaque substance of 

unknown composition. The average length of the 

fibrous elements is 586p, with a range of 335p to 

780p and a MFR of 460p to 700p. 

Vascular rays are uni- and biseriate, with the 

uniseriate rays predominating. Rays make up a large 

portion of the groundmass as viewed in longitudinal 

section. Rays are heterocellular, comprising mainly 

upright and square cell types, the procumbent cell 

type occurs infrequently. Arrangement of the various 

cell types is random. Both the uniseriate and the 

biseriate rays are short, generally ranging from 3 to 

15 cells or more in height. All of the ray cells con- 
NUMBER 5 19 

tain the dark-staining substance found in the fibrous 

elements. 

Axial parenchyma is present in both apotracheal 

and paratracheal arrangement. Apotracheal parenchyma is diffuse and diffuse-in-aggregates and comprises noncrystalliferous strands consisting of two cells 

or more per strand. The paratracheal parenchyma 

is scanty vasicentric to vasicentric, and frequently 

comprises disjunctive cells. Both types of axial parenchyma cells contain the same dark-staining substance present in the fibrous elements and the ray 

cells. An anastomosing arrangement of cells containing this substance is seen in transverse section 

and comprises primarily the diffuse-in-aggregates 

apotracheal parenchyma and rays. 

Vessel elements frequently contain either this darkstaining amorphous substance, or a granular substance, which is similarly stained. Those vessel elements with empty lumens frequently have their cell 

walls coated with this dark-staining substance. 

Discussion 

Since structures which tend to be easily modified in 

response to environmental changes are of relatively 

little taxonomic importance, the choice of characters 

to be studied is critical. In this respect, the components of mature secondary xylem tissue are considered relatively implastic, especially when compared 

with characters of external morphology (Metcalfe 

and Chalk 1950). Of the large number of anatomical characters discernible from study of mature secondary xylem, however, certain characters appear 

to be more plastic than others. Characters incorporating dimensions are, in general, more apt to 

vary with change in environment and growing conditions. The presence or absence of growth rings, the 

lengths of fibrous elements, and the number of vessels 

per unit area are examples of plastic characteristics 

which are usually of little taxonomic significance. On 

the other hand, characters of form or arrangement 

are often less plastic and therefore more significant 

taxonomically. As examples of these, one may cite 

the arrangement of intervascular pitting, the organization of axial parenchyma, and the configuration 

of perforation plates. 

In addition to the relatively implastic nature of 

the anatomical characters of wood, the structure of 

wood tends to be evolutionarily more conservative 

than features of external morphology (Metcalfe and 

Chalk 1950). As a result, differences in the wood 

structure are inclined to be less dramatic than are 

differences in external morphology. Thus, Metcalfe 

and Chalk state that ". . . this [the implastic nature 

of wood structure], combined with its more conservative nature, adds to its value for the study of larger 

groups." 

In addition to being taxonomically valuable as a 

basis of classification, anatomical variations in secondary xylem may reflect the phylogenetic status of 

plant taxa. Although vessel element length may vary 

greatly within different plants of the same species 

and even within the tissues of the same plant, depending upon the age and position of the tissue 

studied (Bailey and Tupper 19 18), vessel element 

length is the most accurate reflection of the fusifom 

cambial initial length (Chalk and Chattaway 1934). 

Bailey and Tupper correlated fusiform cambial initial 

length, as reflected by the length of vascular elements, with degree of evolutionary development 

based on both fossil and extant plants. They found 

that Calamitales, Lepidodendrales, and Cycadofilicales, in addition to extant vascular cryptogams, 

possessed the longest tracheary elements ; gymnosperms, both extant and extinct, possessed tracheary 

elements of intermediate length; and extant dicots 

had the shortest vascular elements. From this classic 

work, based on a large number of plants of wide 

distribution within the extinct and extant tracheophytes, one is led to conclude that a reduction in 

lengh of fusiform cambial initials is associated with 

evolutionary advance (specialization) . Frost ( 1930a, 1930b, 1931 ) , Bailey and Tupper 

(1918), Kribs (1935, 1937), and others correlated 

the lengths of the fusiform cambial initials with other 

features of dicotyledonous xylem anatomy. They concluded that definite trends of specialization accompanied the evolutionary reduction in length of the 

fusiform cambial initials. 

Thus, the systematist, if he so chooses, has at hand 

a tool of great potential taxonomic importance. Using characters derived from the study of wood anatomy as correlative and complementary information, 

he has an independent means of testing presumptive 

phylogenetic relationships. These means are not 

based on the circuitous reasoning commonly encountered in classification based only on morphological characters, e.g., a plant is considered primitive 
SMITHSONIAN CONTRIBUTIONS TO BOTANY 

because it possesses a primitive flower type, which 

itself is considered primitive because it is characteristic of a “primitive” taxon. The seemingly unrelated 

characters of perforation type, end wall inclination, 

intervascular pitting, etc., are now recognized as 

constituting a syndrome or correlative complex useful in reflecting not only form relationship, but the 

evolutionary status of the plant. As Bailey (1957) 

stated, “The chief trends of evolutionary specialization in the cambium and xylem of dicotyledons are 

now so reliably established (except in the case of 

certain patterns of wood parenchyma distribution) 

that they can be utilized to advantage in studying 

salient problems of phylogeny and classification.” 

A final point must be made on the value of xylem 

anatomy in the overall scope of classification. In itself, xylem anatomy is of little inherent value to the 

taxonomists. Bailey (1953) stated that wood structure, as a collection of internal or endomorphic 

characters, is “. . . inherently no more conservative 

or reliable than are exomorphic ones.’’ Any given 

structure or character is not universally plastic or 

implastic; a character which may be implastic and 

thus of taxonomic value within one group of plants, 

may be quite variable and thus of little use in 

another. Thus, endomorphic xylem characters of 

and by themselves, are of no more intrinsic value to 

the taxonomist than are exomorphic characters. 

However, when used in conjunction with other data 

derived from external morphology, in addition to 

other areas of study, xylem anatomy can be of significant value. When utilized by itself, xylem anatomy best serves the taxonomist as a means of negation of relatedness among taxa (Bailey 1957, Cronquist 1968). Because of the ever-present possibility 

that similar structures may result through parallel 

evolution, xylem characters alone cannot be considered as indicative of positive relationship without 

the strong support of supplemental data. 

A brief comparison of the anatomical features of 

the taxa included in this study follows. In general, 

these anatomical features conform well with those 

previously reported in the literature. Some discrepancies are indicated below. 

The single observation of an apparent multiple 

perforation plate in Metopium toxiferum is unique 

in that all other perforations observed in this study 

are simple. Although at least two genera of Anacardiaceae are reported in the literature (Metcalfe 

and Chalk 1950, Heimsch 1942) as having multiple 

perforations in addition to simple perforations 

( Campnosperma and Heeria) , Metopium is reported 

as possessing only simple perforations (Heimsch 

1940). If the perforation observed is indeed a multiple perforation and not a collection of fenestriform 

vessel to parenchyma pits clustered at the end of the 

vessel (as suggested in the description), the occurrence of such multiple perforations is extremely infrequent. Either interpretation leads one to conclude 

that, for all intents and purposes, the xylem of 

Metopium is characterized by simple perforations. 

My observation that Toxicodendron radicans has 

diffuse-porous wood raises some questions. The genus 

Toxicodendron is reported (Heimsch 1942, Metca’fe 

and Chalk 1950, Record and Hess 1943) as having 

generally ring-porous wood. Is the diffuse-porous 

wood of Stern 2633 (Figure 19) a result of environmental factors, or is it simply a feature of immature 

tissue? As noted in the description, the outer growth 

rings exhibit a tendency toward ring porosity. On the 

Florida Keys, T. radicans never has stems that even 

approach the robust stems of this species growing in 

northeastern United States. It is possible that the depauperate growth of the stem on the Keys may have 

some bearing on the formation of ring porosity. The 

climate of the Keys is probably conducive for p!ant 

growth throughout the year. This in itself will have 

an influence on the formation of growth rings and 

may seriously affect the expression of typical ring porosity in this species as it occurs on these islands. 

Spiral thickenings are not present in the vessel elements of T. radicans, although all memberss of the 

genus Toxicodendron are reported (Record 1939) 

as having this feature. Heimsch (1940) reports the 

presence of spiral thickenings in the small vessel 

elements of only T. uernix and the Asiatic T. trichocarpum. Heimsch notes, as a possible explanation 

of this discrepancy, that the portions of the vessel 

element wall occurring between the slitlike intervascular pits and the fenestriform vessel to parenchyma pits give the impression of spiral thickenings 

in unstained or poorly stained sections. My observations agree with those of Heimsch to the extent that 

no spiral thickenings were seen in the specimen of 

T. radicans. 

* Record’s description of the wood characters of the 

genus Toxicodendron is based on specimens of T. diversiloba, 

T. radicans, and T. vernix. 
NUMBER 5 21 

Striking similarities occur among Metopium toxiferum, Toxicodendron radicans, and Bursera simaruba. These s;ecies have fenestriform vessel to parenchyma pit-pairs (Figure 32). Metopium toxiferum 

and Bursera simaruba have medium-sized (in diameter) intervascular pitting. Other species of Pinnatae 

studied have vessel to parenchyma pitting which is 

very similar structurally to the intervascular pitting, 

the intervascular pits ranging in size from small 

to minute in diameter. Metopium toxiferum and 

Bursera simaruba have horizontal intercellular canals 

in their rays (Figure 24). Record (1939) notes that 

these canals occur in Toxicodendron diversiloba, 

although Heimsch (1940) did not observe radial 

canals in any members of the genus. Rays in Metopium toxiferum, Bursera simaruba, Swietenia mahagoni, and the two species of Zanthoxylum are so 

similar as to be hardly distinguishable, except for 

the occurrence of intercellular canals. 

Field collection of the two species of Zanthoxylum 

points up an obvious difference between Z. fagara 

and Z. flavum. Although Z. flavum is reported in the 

literature as possessing wood (heartwood) which is 

". . . exceedingly hard and heavy" (Small 1933), 

having ". . . sp. gr. .90, 56 Ibs./cu. ft." (Record and 

Hess 1943), hand sawing showed that, of the two 

species, Z. fagara was much harder. Upon study of 

the sections of Z. flavum, I was surprised to note 

the presence of thick-walled fibers and a small 

amount of axial parenchyma (as compared with 

Z. fagara, Figures 14, 15), certainly not what one 

would expect of the very soft wood Z. flavum proved 

to be on sawing. Observation of transverse sections 

under crossed nicols reveals, however, that the secondary wall thickenings of the fibrous elements 

of Z. flavum are optically inactive, while those of 

Z. fagara are optically active. This indicated that, 

although the secondary walls of the fibrous elements 

of Z. flavum are lignified (take up safranin stain 

readily), the orientation of the cellulose micelles of 

these secondary walls is such that polarized light 

is not refracted in the transverse plane of section. 

Although not typical in appearance, one could refer 

to these fibrous elements as gelatinous, owing to the 

apparent noncrystalline nature of the secondary wall 

thickenings. The wide occurrence of gelatinous fibers 

could explain the softness of the wood in Z. flavum. 

A character which separates members of the Rutaceae from the other Pinnatae is the presence in 

the rutaceous taxa of at least some radial chain pore 

arrangement (Figure 15). In other Pinnatae, the 

radially oriented pore groups comprised only radial 

multiples (Figure 12). All members of the Rutaceae 

have banded and diffuse axial parenchyma in addition to some paratracheal parenchyma. Swietenia 

mahagoni, Metopium toxiferum, and several members of the Sapindaceae also have this combination of 

axial parenchyma arrangements. Amyris and Citrus 

have enlarged crystalliferous idioblasts (Figure 25), 

as does Dodonaea of the Sapindaceae. The occurrence of crystals in either ray parenchyma or axial 

parenchyma is a nearly universal character of the 

species studied. Only Metopium toxiferum, Toxicodendron radicans, and Suriana maritima lack such 

crystals. 

Although the xylem anatomy of Cardiospermum 

halicacabum is not described in the literature 

(Heimsch 1942, Metcalfe and Chalk 1950, Record 

and Hess 1943), the xylem of two genera (Serjania 

and Paullinia) of sapindaceous lianas are described. 

The occurrence of two distinct vessel element types 

in Cardiospermum (Figure 35) noted above conforms with the descriptions of vessel elements given 

for Serjania and Paullinia (Heimsch 1942, Metcalfe 

and Chalk 1950). The presence of dimorphic vessel 

elements is likely related to the lianous habit in this 

family. 

Throughout this investigation, various anatomical 

characteristics were evaluated, with the hope that1 

a significant set of these could be found which might 

reflect the present familial arrangement of the 16 

species studied. Although certain families did possess 

anatomical features which served to identify their 

members, other families did not possess such unifying features. However, all the members of Pinnatae 

do exhibit many anatomical characters in common 

to indicate that we are dealing with a remarkably 

homogeneous group of plants. 

Comparison among families of Pinnatae of those 

anatomical characters considered to be of greatest 

taxonomic and phylogenetic significance by Metcalfe 

and Chalk (1950) reveals that (1) all members 

possess vessel elements having simple perforations, 

(2) the vessel elements of all members have alternately arranged intervascular pitting, (3) all members possess fibers with slitlike simple to slightly 

bordered pits, and (4) all members possess at least 

paratracheal axial parenchyma, with the banded 
22 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

configuration (paratracheal and apotracheal) the 

most common. Although anatomical differences exist 

among the 16 species studied, none of these is great 

enough to warrant the exclusion of any one of the 

members from this group. By and large, greater 

anatomical differences are seen to exist among genera within the same family (e.g., SapindaceaeTable 4) and even among species of the same genus 

(e.g., Zanthoxylum-Table 4), than exist among 

the families represented in this group. 

Although the ray structure encountered in this 

study varies in regard to cellular makeup (heterocellular as opposed to homocellular, uniseriate as 

opposed to multiseriate) , the relative sizes of the 

rays of each species are similar. The rays of species 

having only uniseriates are low, rarely exceeding 

2OOp in height. Those rays in species having multiseriates are also low, rarely exceeding 600p in height. 

The widest multiseriate rays do not exceed 10 cells 

(loop) in width. 

Looking at anatomical characters which vary 

within the group as a whole, but remain relatively 

constant at the family level, we find an interesting 

and significant segregation. The nature of the vessel 

to parenchyma (both axial and ray) pitting is remarkably consistent among the 15 genera, with the 

three exceptions of Bursera, Metopium, and Toxicodendron. Only Bursera and Metopium of the 15 

TABLE 4.-Summary of xylem anatomical data in the "Pinnatae" 

SPECILS 

ANACAFDIACEAE 

Metapiir. toxife?wi 

Toxicade?.dron radicans 

BURSEFACEAE 

__- B~rsera sisaruba 

TZLIACFAE 

Swietenia mhegoni 

RUTACEAE 

Amyris elernifera 

Citm6 aurantiifolia 

Zanthaxyllun 

2. fl8"Ul 

SApINDACEbi 

_- 

Cardiospemm halicesabm 

Cupacia glabra 

~__ Jkdanaea viscose 

panim1ata 

melate trifoliata 

Sepindus sapoIia?ia 

SDNLROUBACEAE 

Simmuba glauca 

-- Suriana maritima 

42 4 u 

ri 

y11 

> .5 

L, 

4: 

;2 

- 

375 

253 

531 

'137 

25c 

273 

261 

515 

200 

414 

234 

426 

319 

278 

446 

173 

- 

- 

- ELEK 

ci 

J 

u 

ria 

OJri mac 

ma Loo 

GI- 

>d 

2: 

?$ 

ma 

- 

4ir 

41 

48 

62 

55 

58 

64 

44 

76 

44 

54 

43 

'17 

62 

6c 

63 

- 

- 

- S 

i 

ri 

a 

n" 

42 

3.4 

5 

:% 

u r N i 

- 

0)- .i 

medim 

Small 

rnediwr. 

nin-te 

sinute 

srnE.11 

minute 

small 

small 

minute 

minure 

minute 

minute 

m.ir.use 

small 

minute 

B, Al, C 

D, s, v 

S 

B, #, S, 'J 

C, A1 

D, s, v 

1,2,1,~ het 

1, horn. 

L,3,ZnL, het 

L33,het. 

1,33,het. 

'Classification of intervascular pitting follows that swgested by Record snd Chattaway (19?9). 

bUnderlined nurr.bers indicate the predominant ray type (2 = tPiEeriste rays most freqilent ). 

*Xembers having Septate fibrous elements which contain starch. 
NUMBER 5 23 

genera possess intervascular pits of medium size, the 

other 13 genera have either small or minute pits. 

Four genera possess heterocellular multiseriate rays 

having uniseriate wings, and among them are Bursera and Metopium. Add to this the horizontal intercellular canals in the rays of both Bursera and Metopium, and one recognizes that the members of the 

Florida Keys Pinnatae may be subdivided on the 

basis of xylem anatomy so that the genera of Anacardiaceae and Burseraceae are by and large distinguishable from the other genera. 

Phylogenetic interpretation of the data derived 

from this study indicates that the woods of the 16 

species exhibit a high degree of specialization. The 

syndrome of short to medium length vessel elements, 

simple perforation plates, alternate intervascular pitting, and absence of steeply inclined vessel element 

end walls shows that the members of the Pinnatae 

studied are at approximately the same relatively 

advanced level of specialization. In addition, the 

storied structure, found in Simarouba and Swietenin 

(Figure 23), represents another line of specialization 

which occurs only in certain Pinnatae. Kribs (1935) 

considered woods having either homocellular rays 

(Amyris and Sapindus) or strictly uniseriate rays 

(Amyris, Cupania, and Hypelate) as highly advanced. The rays of Suriana are, for all intents and 

purposes, uniseriate. Heterocellular rays which are 

made up in large part of procumbent cells, with 

the square and upright cells, or both, occurring only 

sporadically and infrequently (Citrus and Simarouba) , are also considered as relatively advanced. 

The common ray configuration (procumbent cells 

comprising the multiseriate portion with upright' 

and square uniseriate wings or both) seen in Metopium, Bursera, Swietenia, and Zanthoxylum, in addition to the low rays found in the remainder of 

the genera, constitutes an advanced ray situation. 

The presence of various aggregate arrangements of 

axial parenchyma, such as banded, aliform and 

confluent, or both (only Toxicodendron, Bursera, 

and Suriana lack such arrangements), is accepted 

as being advanced. The occurrence of fibrous elements lacking distinctly bordered pits is also an 

advanced characteristic. 

The wide occurrence of starch grains in the parenchymatous tissue of the specimens studied probably is of little taxonomic significance. However, 

specimens of Toxicodendron, Bursera, Exothea, and 

Cardiospermum have septate fibrous elements that 

contain this storage product (Figures 12,13,24,29) . 

This feature may be of some taxonomic import in 

that it is correlated with a relatively small amount 

of axial parenchyma in these taxa. This observation 

is in agreement with those of Harrar ( 1946). 

The occurrence of septate fibrous elements appears 

to be a local phenomenon and is of little taxonomic 

significance in this group (the Pinnatae) . The only 

families that have members lacking septate fibers, 

based on the species in this study, are Rutaceae and 

Simaroubaceae. Both of these families, however, have 

other members that have septate fibers (Metcalfe 

and Chalk 1950). 

The taxonomic value of diffuse-porosity is also 

questionable, The effect of environment on the 

topography of wood is not certain. The great majority of tropical trees having distinct growth rings 

possess woods that are diffuse-porous, and the OCcurrence of ring-porosity is largely restricted to woody 

plants of the North Temporate Zone (Gilbert 1940). 

The fact that all members, with the possible excep-, 

tion of Toxicodendron, have diffuse-porous wood is 

thus of debatable taxonomic value here. 

A survey of the literature (Metcalfe and Chalk 

1950), concerning both morphological and anatomical characteristics of the families concerned with in 

this study, shows that the occurrence of secretory 

structures (Figures 24-27) characterizes members 

of the Pinnatae. The intercellular canals of anacardiaceous and burseraceous woods, and the intercellular canals in the bark and pith of these families, 

as well as Simaroubaceae and Sapindaceae, are 

examples of such structures. Secretory cells are reported as occurring in the pith and cortex of all 

families. The occurrence of pellucid glands in the 

leaves of Rutaceae is well known. In addition, traumatic axial canals are reported to occur either frequently or sporadically in some members of all families, with the exception of Sapindaceae and Anacardiaceae. The widespread presence of dark-staining, gumlike substances in the parenchyma and 

vessels of many of the species seen in -this study 

(Figures 20,22) suggests the secretory potential of 

these members. The traumatic axial canal observed 

in Zanthoxylum fagara also contained a darkly staining deposit. Crystals, which occur widely in the 

xylem of Pinnatae are products of idioblasts. These 

too are considered as secretory cells. Thus, the oc- 
SMITHSONIAN CONTRIBUTIONS TO BOTANY 

currence of secretory structures in most, if not all 

members, may be of taxonomic value; insofar as it 

might serve as another indication of the homogeneous 

nature of Pinnatae. 

The data derived from this study indicate that 

the Pinnatae constitute a homogeneous group, and 

that no anatomical basis exists for segregation of the 

various members into separate orders. The traditional 

Englerian separation of the Sapindaceae and Anacardiaceae from the remainder of the families is not 

supported by xylem anatomy. Hutchinson’s separation of the families into three orders, and Takhtajan’s and Thorne’s separation of Sapindaceae from 

the other families, likewise, have no anatomical basis. 

Cronquist’s treatment most nearly reflects the anatomical similarities that exist, with the exception 

that he removes Suriana from the Simaroubaceae 

and places it into the Stylobasiaceae. There is no 

anatomical foundation for the separation of Suriana 

from the Simaroubaceae. This conclusion is based 

both on data derived from this study and the anatomical literature (Webber 1936). Cronquist’s (1968) 

assignment of Suriana and Stylobasium to his Stylobasiaceae is based on characters of habit and morphology, and a complete study of the anatomy of 

Stylobasium and Suriana must be carried out before 

such an association can be anatomically evaluated. 

The inclusion of Anacardiaceae and Burseraceae in 

the single family Terebinthaceae, as proposed by 

Hallier (1912), is supported by xylem anatomy. 

Summary 

A study of the wood of 16 species of Florida Keys 

Pinnatae indicates that the group is anatomically 

homogeneous. All members possess simple perforation plates, vessel elements having alternate intervascular pitting, fibrous elements with small slitlike, 

simple to vestigially bordered pits, and axial parenchyma which is both apo- and paratracheal. 

Crystals are of wide occurrence in the parenchyma 

cells, and banded and aliform to confluent parenchyma occur in several taxa. Certain families or 

groups of families have unique characters : radial 

chain arrangement of pores in the Rutaceae, random 

arrangement of cells in the heterocellular ray types 

among members of the Sapindaceae, and fenestriform 

vessel to parenchyma pit-pairs and intercellular canals in the rays of Anacardiaceae and Burseraceae. 

The only separation of families within Pinnatae 

suggested by a syndrome of several unique characteristics is the formation of an Anacardiaceae-Burseraceae complex. These characteristics, however, 

when viewed in light of the many common features 

of the families, are not sufficient bases for the separation of the Anacardiaceae and Burseraceae from 

the Pinnatae as a group. 

There is no anatomical basis for the separation 

of families into distinct orders as proposed by Engler, 

Hutchinson, Takhtajan, and others. The system of 

classification proposed by Cronquist is anatomically 

feasible except for his exclusion of Suriana from the 

Simaroubaceae. The members of the Pinnatae are 

seen by this author as belonging to a taxon corresponding well with Cronquist’s Sapindales. 

Phylogenetically, the Pinnatae constitutes an advanced taxon. Simple perforation plates, short to 

medium length vessel elements having alternate intervascular pitting, slightly inclined vessel element 

end walls, advanced ray types, fibrous elements with 

simple or vestigially bordered pits, and the predominant banded and confluent axial parenchyma mark 

the Pinnatae anatomically as a highly specialized 

group. The possession of storied rays in two species 

is another trend of specialization. 

Based on the data derived from this anatomical 

study and from the literature, the 16 species of 

Florida Keys Pinnatae are members of a homogeneous, phyletically advanced group. Furthermore, that 

this group constitutes a genetically related complex 

of plants is borne out by correlative studies in floral 

and vegetative morphology, as well as by the substantial anatomical studies of which this investigation is a part. These members belong in the Sapindales as described by Cronquist. 

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Bailey, I. W. 
NUMBER 5 25 

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Chalk, L. 

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Chalk, L., and M. M. Chattaway 

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SMITHSONIAN CONTRIBUTIONS TO BOTANY 

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191 1. Surianaceae. North American Flora 25 :225. 
NUMBER 5 

FIGURE 1-4-1, Toxicodendron radicans: habit showing flowers; 2, Bursera simaruba: habit 

indicating size of tree; 3, Bursera simaruba: leaves and fruit; 4, Swietenia nahagoni: habit indicating size of tree. 

27 
28 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

FIGURES 5-8.-5, Zanthoxylum flavum: leaf showing glandular dots; 6, Sapindus saponaria: 

habit with fruits and leaves (note winged rachis of pinnately compound leaves) ; 7, Sapindus 

saponaria: fruits; 8, Cardiospermum halicacabum: habit with fruits and flowers. 
NUMBER 5 

FIGURES 9-1 1.-9, Cupania glabra: fruits and leaves; 10, Simarouba glauca: flowers; 11, 

Suriana maritima: flowers (note simple leaves). 

29 
30 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

FIGURES 12-15.-12, Bursera simaruba: transverse section showing radial multiples and solitary 

pores (note starch in the fibers), X 246; 13, Bursera simaruba: transverse section viewed 

under crossed nicols (polarized light) showing the birefringent property of the cell walls and 

starch grains, X 269; 14, Zanthoxylum fagara: transverse section showing banded parenchyma 

and radially oriented pore multiples and chains, X 269; 15, Zanthoxylum fiavum; transverse 

section showing large amounts of thick-walled fibers. Banded parenchyma and radially oriented 

pore multiples and chains are also shown (note the presence of starch grains in both ray and 

axial parenchyma), X 269. 
NUMBER 5 31 

FIGURES 16-19.-16, Cupania glabra: transverse section showing growth rings, and solitary, 

radial multiples, and clusters of pores, X 109; 17, Simarouba glauca: transverse section showing aliform and confluent parenchyma arrangement, X 97 ; 18, Sapindus saponaria: transverse 

section showing confluent bands of parenchyma, X 97 ; 19, Toxicodendron radicans: transverse. 

section showing qdestionable diffuse-porous distribution of pores, X 246. 
32 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

FIGURES 20-23.-20, Cupania glabra: radial section showing randomly arranged procumbent, 

square and upright cells. Note the gumlike substance in ray cells, X 390; 21, Metopium 

toxiferum: Tangential section showing rays having uniseriate “wings,” X 246; 22, Swieteniu 

mahagoni: Radial section showing rays having square and upright, or both, marginal cells, X 

97; 23, Simarouba glauca: tangential section showing the storied arrangement of rays and axial 

strand parenchyma, X 97. 
NUMBER 5 33 

FIGURES 24-27.-24, Bursera simaruba: tangential section showing intercellular canals in the 

rays (note the starch grains in the septate fibers), X 269; 25, Citrus aurantiijolia: radial section showing enlarged crystalliferous idioblasts, X 539 ; 26, Zanthoxylum fagara: Transverse 

section showing traumatic intercellular canal, X 269 ; 27, Zanthoxylum fagara: radial section showing the traumatic intercellular canal in longitudinal section, X 539. 
34 SMITHSONIAN CONTRIBUTIONS TO BOTANY 

FIGURES 28-32.-28, Exothea paniculata: radial section showing slitlike simple to slightly 

bordered fiber pits in face view (arrow), X 1872; 29, Exothea paniculata: tangential section 

showing the fiber pits in transverse section (arrow). Note starch grains, X 1872; 30, Citrus 

aurantiifolia: tangential section showing alternate intervascular pitting. Note the coalescence 

of adjacent pit apertures (arrow), X 734; 31, Metopium toxiferum: tangential section showing unilaterally compound intervascular pittings (arrow), X 1872 ; 32, Bursera simaruba: 

maceration showing the occurrence of fenestriform vessel pitting. These pits occur in the cell 

walls of both vessel elements and parenchyma. Note the simple perforation plate, X 269. 
NUMBER 5 35 

FIGURES 33-35.-33, Amyris elmifera: radial section showing tyloses and granular, translucent 

material in the vessel elements, X 292; 34, Metopium toxijerum: transverse section showing 

tyloses in vessels and the occurrence of gelatinous fibers, X 269; 35, Cardiospermum halicacabum: transverse section showing large solitary pores and radial multiples of small angular 

pores (arrow), X 269. 

* U.S. OOVERNMCNT PRlNTlNQ OFFICE: 1972-417--398/12