bluuebunny/crossref_metadata_2025 huggingface dataset:
ESTABLISHMENT OF THE VASCULAR SYSTEM IN SEEDLINGS OF POPULUS DELTOIDES BARTR.
Authors: Larson Philip R.
Published: January 2018

Seven seedlings ranging from 1 to 25 days old were embedded in Spurr's resin and serially sectioned at 1–2 μm. Sectioning extended from well above the apex downward to the hypocotyl base in the 1–day seedlings and to varying levels in the hypocotyl in the older seedlings. Procambial development was analyzed in its entirety for each seedling, and a composite two‐dimensional diagram representing the procambial system of a 25‐day‐old seedling was prepared. Each cotyledon was served by a double‐trace, one‐half of which was derived from each of two embryonic bundles. The central traces serving the four primary leaves were in turn derived from the four cotyledonary bundles comprising the double traces. The procambial system serving the cotyledons and the four primary leaves approximated a decussate phyllotaxy. The central traces serving the secondary leaves were arranged in a helix that conformed at first to a 1/3 and then to a 2/5 phyllotaxy. Transitions to higher phyllotactic orders were systematic and reproducible, and they occurred in an orderly sequence in both the central and lateral leaf traces. The manner in which leaf traces diverged from parent traces to serve new leaf primordia provided for vascular redundancy. Thus, the entire vascular system was integrated into a highly functional whole.
EFFECTS OF LIGHT AND HORMONES ON REGENERATION OF CRASSULA ARGENTEA FROM LEAVES
Authors: Paterson Karol E. , Rost Thomas L.
Published: January 2018

Plantlet regeneration from leaf segments of Crassula argentea was studied under variable light and hormone treatments. The effects of two hormones (indole 3‐acetic acid and isopentenyl adenine at 10−4 to 10−10 m) and photoperiods of 8 (short days) or 16 hr of light (long days) were examined. Exogenously applied hormones had little stimulating effect on regeneration but were consistently inhibitory at 10−4 m. Short days and continuous darkness caused the greatest promotion of regeneration. Prolonged short‐day growth periods prior to culturing caused an increasingly greater regeneration response.
PALYNOLOGICAL STUDIES OF GAYA AND HERISSANTIA (MALVACEAE)
Authors: Hanks Sharon , Fryxell Paul A.
Published: January 2018

This study compares Herissantia tiubae with 10 species of Gaya H.B.K., and Herissantia Medicus. The pollen morphology of the eleven species is described in detail by observations from both the scanning electron and light microscopes. The palynological data were used to produce pollen descriptions and a phenogram based on similarity coefficients. This information was combined with morphological and cytological data to determine the taxonomic relationship and proper placement of H. tiubae, which has the pollen characteristics of Herissantia and is properly placed in that genus.
HEARTWOOD FLAVONOIDS AND THE INFRAGENERIC RELATIONSHIPS OF RHUS (ANACARDIACEAE)
Authors: Young David A.
Published: January 2018

Heartwood flavonoids of 23 taxa of Rhus L. were surveyed in order to assess infrageneric relationships and classification. Fourteen flavonoids and two coumarins were detected in the heartwood extracts. All taxa were characterized by a flavonoid complement consisting of eight 5‐deoxyflavonoids involving several aglycone classes (e.g., flavonols, flavones, aurones, chalcones and dihydroflavonols) and the aurone rengasin. None of the 5‐hydroxyl analogs of the 5‐deoxyflavonoids were detected in the heartwood extracts. Infraspecific flavonoid patterns were uniform in different populations, although the presence of 3′,4′‐dihydroxyflavone 4′‐O‐β‐glucoside varied in some taxa. Taxa of Rhus subgenus Rhus consistently differed from all taxa of Rhus subgenus Lobadium in lacking glycosides of fisetin, butein and 3′,4′‐dihydroxyflavone. The major evolutionary trend in the heartwood flavonoids of Rhus appears to be accumulation of simple mono‐ or diglucosides. Data from heartwood flavonoids suggest that Rhus be treated as consisting of two subgenera (Rhus and Lobadium) and that subgenus Lobadium be divided into three sections.
THE PHLOEM OF ETAPTERIS LECLERCQII AND BOTRYOPTERIS TRIDENTATA
Authors: Smoot Edith L.
Published: January 2018

The phloem of Etapteris leclercqii and Botryopteris tridentata petioles is described from Lower Pennsylvanian coal balls. Petioles of B. tridentata are characterized in transverse section by an omega‐shaped xylem trace, a phloem zone which extends from 2‐10 cells in width, and 2‐parted cortex. Etapteris leclercqii petioles exhibit a 4–9 cell‐wide phloem zone surrounding the central clepsydroid xylem mass, and a 3‐parted cortex. In both taxa a 1–2 cell layer parenchyma sheath separates the xylem from the extra‐xylary tissues. The phloem of both species consists of sieve elements that average about 20 μm in diam by 200 μm in length in Botryopteris, and 100 μm in length in Etapteris, with horizontal‐slightly oblique end walls. In transmitted light, the radial walls of the sieve elements form an irregular reticulate pattern enclosing elliptical lighter areas. With the scanning electron microscope, these areas appear as horizontal‐slightly oblique furrows on the cell wall, with many small indentations lining the furrows. These indentations, because of their regular occurrence and size (from a few fractions of a micron up to 1.0 μm in diam), are interpreted as sieve pores, and the elliptical areas that enclose them as sieve areas. The phloem of E. leclercqii and B. tridentata is compared with that described for other fossil genera and with that of extant ferns.
MORPHOMETRIC ANALYSIS OF POLLEN FROM FOUR SPECIES OF AMBROSIA (COMPOSITAE)
Authors: Robbins R. R. , Dickinson D. B. , Rhodes A. M.
Published: January 2018

A morphometric approach proved useful for characterizing pollen from the Ambrosia species that are responsible for most ragweed hayfever and for correctly identifying individual pollen grains. Pollen was harvested from 4 species (A. trifida, A. artemisiifolia, A. bidentata, A. psilostachya) grown in Champaign County, Illinois, and observed with a scanning electron microscope. Quantitative measurements of 6 different exine characters were made on micrographs of 96 pollen grains from each species. Discriminant analysis based on these characters was used to obtain a population centroid for each species and indicated that these centroids were distinctly different. This analysis also included a species classification for individual pollen grains and indicated probability of species membership. About 86% of all individuals were correctly classified when the 4 species were included, with a range from 80% (A. artemisiifolia) to 95% (A. psilostachya). When three species (A. trifida, A. artemisiifolia, A. bidentata) were analyzed, about 87% of the individuals were correctly classified, and almost all individuals (97%) were classified correctly when only A. trifida and A. artemisiifolia were included. The validity of the derived discriminant functions was also tested by treating herbarium specimens as unknowns. The species and percentages of these individuals correctly classified were A. trifida (100%), A. artemisiifolia (58%), A. bidentata (100%), and A. psilostachya (31%). The classification results using three species were A. trifida (100%), A. artemisiifolia (75%), and A. bidentata (100%); and using two species were A. trifida (100%) and A. artemisiifolia (92%). Hence, the disciminant functions do seem valid for 3 species, but further investigation of A. psilostachya is needed. This type of approach may be useful in pollen analysis, especially where these species significantly contributed to aeroallergens.
SPORE WALL ULTRASTRUCTURE IN FOUR SPECIES OF THE LIVERWORT RICCIA
Authors: Steinkamp M. P. , Doyle W. T.
Published: January 2018

Mature spores ofRiccia californica, R. campbelliana, R. sorocarpa, andR. trichocarpa(Marchantiales, Ricciaceae) were examined with both scanning and transmission electron microscopes. The thick‐walled spores have species‐specific surface sculpturing and similar internal structure. Major surface features include ridges and depressions in areolate or irregular configurations. Finer surface features such as tubercles or papillae may ornament the ridges or depressions. Internally, the sporoderm consists of a thin intine and a three‐layered, lamellate exine. The innermost exine lamellae are thin and closely spaced, giving this layer a fibrillar appearance. Lamellae of the middle region are thick in section and have a relatively thick, electron‐dense coating. The outermost lamellae are of intermediate thickness and also have a relatively thick electron‐dense coating. Lamellae of all regions frequently split, branch and anastomose. The outermost lamella forms the surface features of the spore. Interior lamellae follow the contour of the outermost lamella. Pores usually occur in these four species at the junctures of the triradiate ridge arms and equatorial rim. Pores do not penetrate the entire exine, and they represent localized areas where the outermost group of lamellae have not been formed.
EXPERIMENTAL INITIATION OF HAUSTORIA IN AGALINIS PURPUREA (SCROPHULARIACEAE)
Authors: Riopel James L. , Musselman Lytton J.
Published: January 2018

The initiation and early developmental stages of the haustorium were studied in Agalinis purpurea (Scrophulariaceae). Plants were grown in a 0.9% agar inorganic medium with a 0.5% sucrose supplement. Root exudate collected from Lespedeza sericea induced the initiation of haustoria, with earliest stages evident in 6‐12 hr. A 30‐min exposure to exudate produced an increased frequency of haustoria and a 24‐hr exposure yielded haustorial frequencies equal to the number that were initiated on control plants continuously exposed to root exudate for the 5‐day growth period. The early cytological features of haustorial development are described and the possible significance of haustorial initiation in host recognition is discussed.
STOMATA ON THE FRUITS AND SEEDS OF ESCHSCHOLZIA (PAPAVERACEAE)
Authors: Jernstedt Judith A. , Clark Curtis
Published: January 2018

Stomata are present on the outer and inner fruit walls and seed coats of Eschscholzia californica, E. covillei, E. glyptosperma, E. lemmonii and E. minutiflora. The stomata on the inner fruit wall and seed coat remain constantly open, even under plasmolyzing conditions, whereas those of the outer fruit wall are able to open and close. This allows for gas exchange in these chlorophyllous structures. Fibrous bundle caps in the costal regions of the fruit act as windows allowing light transmission to the photosynthetic seeds within. Preliminary results show that the total photosynthesis by the fruits and seeds of Eschscholzia californica together appears to at least balance respiratory losses, and under favorable conditions might significantly contribute to seed and fruit development.
FLORAL ONTOGENY OF ILLICIUM FLORIDANUM, WITH EMPHASIS ON STAMEN AND CARPEL DEVELOPMENT
Authors: Robertson Richard E. , Tucker Shirley C.
Published: January 2018

The ontogeny of the flower and fruit of Illicium floridanum Ellis, the Star Anise, was investigated. Each of 5 or 6 bracts in each mixed terminal bud subtends either a vegetative or floral bud. The solitary flowers occur in terminal or axillary positions. Each flower has 3–6 subtending bracteoles arranged in a clockwise helix. The flowers in our material have 24–28 tepals, 30–39 stamens, and usually 13 (rarely 19) uniovulate carpels. Tepals and stamens are initiated in a low‐pitched helix; carpels later appear whorled, but arise successively at different levels on the apical flanks. The floral apex is high‐convex in outline with a tunica‐corpus configuration; it increases in height and width throughout initiation of the floral appendages. Tepals, stamens, and carpels are initiated by one to several periclinal divisions in the subsurface layers low on the apical flanks, augmented by cell divisions in the outer layers of the corpus. The carpel develops as a conduplicate structure with appressed, connivent margins. Procambium development of floral appendages is acropetal and continuous. Bracteoles, tepals, stamens and carpels are each supplied by 1 trace; the carpellary trace splits into a dorsal and an ascending ventral sympodium. The latter bifurcates to form 2 ventral bundles. The ovular bundle diverges from the ventral sympodium. Ovule initiation occurs in a median axillary position to the carpel, an unusual type of ovule initiation. The fruit vasculature is greatly amplified as the receptacle and follicles enlarge. After carpel initiation an apical residuum persists which is not vascularized; a plate meristem develops over its surface to produce a papillate structure.
TRIPLOCHITIOXYLON (STERCULIACEAE): A NEW GENUS OF WOOD FROM THE EOCENE OF OREGON AND ITS BEARING ON XYLEM EVOLUTION IN THE EXTANT GENUS TRIPLOCHITON
Authors: Manchester Steven R.
Published: January 2018

A new sterculiaceous wood, Triplochitioxylon oregonensis gen. et sp. n., was collected from a Middle Eocene locality in the Clarno Formation of Oregon. Anatomical data indicate a close natural relationship between T. oregonensis and the living species of Triplochiton, a genus endemic to tropical Africa. The fossil is believed to represent a population of the group or complex from which Triplochiton evolved. The basic differences in the xylem organizations of the two genera are explained by a significant reduction of fusiform initial length and by a complete suppression of post‐cambial parenchyma strand elongation in the extant genus. Paleobotanical and biogeographical evidence suggest that the xylem evolution has been strongly influenced by the increasing aridity of the African continent.
CROSSING RELATIONSHIPS AMONG DIPLOID SPECIES OF THE SOLANUM NIGRUM COMPLEX IN NORTH AMERICA
Authors: Schilling Edward E. , Heiser Charles B.
Published: January 2018

Crosses were made in all combinations of the six diploid species of the Solarium nigrum complex that occur in North America. Some interspecific pollinations failed to yield viable seed; successful crosses gave rise to moderately to highly sterile F1 hybrids. Results of interspecific crosses suggested phylogenetic relationships that were not completely in accord with those suggested by morphology. Interspecific crosses also gave varied results. All interpopulational crosses within S. interius and S. sarachoides produced fully fertile hybrids. In contrast, hybrids within S. americanum and S. douglasii varied from fully fertile to almost completely sterile. Populations of S. pseudogracile could be divided into two groups which are geographically separated but not morphologically differentiated. Fully fertile hybrids resulted from crosses within a group, whereas crosses between groups gave hybrids with reduced fertility. Four crossing groups were observed within 5. nodiflorum; three of the parental groups are sympatric and are morphologically differentiated. Although hybrid sterility in interspecific crosses is sometimes used to support delimitation of species, the presence of sterility in intraspecific crosses suggests that such an interpretation is unwarranted for the S. nigrum complex. Hybrid sterility, therefore, is not considered to have special taxonomic significance in this complex.
A TETRAHEDRAL MEGASPORE ARRANGEMENT IN A SEED FERN OVULE OF PENNSYLVANIAN AGE
Authors: Schabilion J. T. , Brotzman N. C.
Published: January 2018

A tetrahedral arrangement of one functional and three aborted megaspores has been found in the fossil seed fern ovule Conostoma anglo‐germanicum. This is the first conclusive report of a Pennsylvanian age ovule with such a primitive megaspore arrangement, suggesting that this feature was more widespread and persistent among Paleozoic pteridosperms than previously assumed.
VEGETATION AND FLORAL COLORS REVEALED BY ULTRAVIOLET LIGHT: INTERPRETATIONAL DIFFICULTIES FOR FUNCTIONAL SIGNIFICANCE
Authors: Kevan Peter G.
Published: January 2018

The importance of measuring floral colors as insects might see them is often ignored. Ultraviolet, only one of the wavebands visible to insects, is often recorded in vacuo, without reference to the insect visual spectrum, without quantification, and without reference to background coloration and ambient lighting. Such oversights may lead to serious errors in interpreting the functional significance of floral colors and color patterns.
FACTORS DETERMINING VARIOUS FORMS IN CLADOSIPHON ZOSTERAE (PHAEOPHYCEAE)
Authors: Lockhart Joan Conway
Published: January 2018

The brown alga Cladosiphon zosterae (J. Ag.) Kylin (Chordariaceae) is found to exist in culture in a variety of forms, including filaments, discoid or crustose forms, and two types of erect cylindrical thalli. Asexual spores from plurilocular sporangia of each form can produce any and all forms. Three factors controlling morphological expression in C. zosterae have been identified. These factors include: (1) heteroblasty (formation of filamentous and discoid germlings as a consequence of alternate modes of spore germination), which was independent of all environmental factors tested including temperature, photoperiod, nitrogen source, and general fertility of the growth medium; (2) influence of certain nitrogen sources, notably ammonium, which induce a compact discoid or crustose form; and (3) a morphogenetic factor presumed to be bacterial which determines mode of development and subsequent morphology of the erect Cladosiphon thallus.
ULTRASTRUCTURE OF THE DINOFLAGELLATE PERIDINIUM CINCTUM F. OVOPLANUM. I. VEGETATIVE CELL ULTRASTRUCTURE
Authors: Spector D. L. , Triemer R. E.
Published: January 2018

Vegetative cells ofPeridinium cinctum f. ovoplanumhave a dense cytoplasm containing those organelles characteristic of eukaryotic cells. Thecal plates have a fibrillar substructure with numerous 200‐nm pores. Chloroplasts are radially arranged and contain a simple internal pyrenoid. An eyespot is associated with the chloroplast. The large, centrally located nucleus contains over 100 chromosomes dispersed in a granular nucleoplasm. Chromosomal bands with a periodicity of 86 nm are present perpendicular to the long axis of the chromosome. Numerous chromosomes are attached to the nuclear envelope.Peridinium cinctumvegetative cell morphology is compared to other dinoflagellates examined.
STEWARTIOTHECA GEN. N. AND THE NATURE AND ORIGIN OF COMPLEX PERMINERALIZED MEDULLOSAN POLLEN ORGANS
Authors: Eggert D. A. , Rothwell G. W.
Published: January 2018

Stewartiotheca gen. n. is a bell‐shaped, unisynangiate pollen organ with eccentric radial symmetry and a single series of about 80 pollen sacs. Infoldings that vary in depth occur circumferentially and extend from the periphery to a point off center. This position also marks the location of a sclerenchyma column (proximally) and a sclerenchyma‐lined, conical hollow (distally) that opens onto the distal face of the organ. Plates of ground parenchyma extend inward from the outer covering of the organ at locations of infoldings, while similar plates with sclerenchyma strands occur between these locations. Pre‐pollen of Monoletes type was released through distal longitudinal slitlike openings of the pollen sac faces toward the sclerenchymatous ground tissue plates. Vascular bundles entering the organ undergo repeated dichotomies, and lead to numerous bundles both in the cover (one per sac for those sacs that abut directly on cover tissue) and internally (one per pair of pollen sacs that lie opposite one another across the location of an infolding). The most complex permineralized medullosan pollen organs Sullitheca, Stewartiotheca, and Dolerotheca are considered to have evolved from a similar type of cup‐shaped organ with a single ring of pollen sacs, broadly open distally, and with a central hollow. Circumferential infoldings of one organ of this type were involved in the origin of both Stewartiotheca and Sullitheca, while four similar organs, each showing infoldings non‐circumferentially, fused to produce the Dolerotheca type organ (exemplified by D. formosa), a compound synangium.
DEVELOPMENTAL ASPECTS OF ROOTS OF PISUM SATIVUM INFLUENCED BY THE G2 FACTOR FROM COTYLEDONS
Authors: Evans Lance S.
Published: January 2018

A G2 Factor present in cotyledons of Pisum sativum influences several developmental events in roots. G2 Factor present in dry seeds (cotyledons and radicles) is transported to roots after germination and promotes cell arrest in G2 in about 35% of all root meristem cells. Present evidence suggests the G2 Factor promotes cell arrest in G2 only in cells that undergo normal cell differentiation (arrest) because the proportion of cells labeled with 3H‐TdR after 16 hr does not differ among both seedlings or excised roots in the presence or absence of this substance. In this manner, trigonelline differs from chalones of animal tissues that usually suppress cell proliferation by cell arrest either in G1 or in G2. Experimental results suggest that cortex cells and not cells of vascular tissues in mature root tissues (20–22 mm from the meristem) are influenced by G2 Factor. Other recent publications indicate that the G2 Factor is trigonelline (N‐methyl nicotinic acid) and concentrations of synthetic trigonelline from 10−5 to 10−7 m are effective in promoting cell arrest in G2 in one of the G2 Factor bioassays.
THE OCCURRENCE AND PHYLOGENETIC SIGNIFICANCE OF A MULTILAYERED STRUCTURE IN COLEOCHAETE SPERMATOZOIDS
Authors: Graham Linda E. , McBride Gordon E.
Published: January 2018

Spermatozoid‐forming cells ofColeochaete scutatawere found in packets of four arranged in concentric internal bands. Spermatozoids, which occur singly in antheridial cells, are spherical to ovoid, approximately 7 μm long by about 3.9 μm wide. As compared to relatively unspecialized zoospores, male gametes undergo a number of specialized cellular changes during development. The spherical nuclei and cytoplasm of mature spermatozoids are increased in density. Posterior plastids are reduced and contain large starch grains. Many small mitochondria are clustered near the cell anterior. The plasmalemma is covered with a layer of flattened, diamond‐shaped scales, while body scales of zoospores are pyramidal. The two flagella of both zoospores and spermatozoids are covered with flattened, diamond‐shaped scales and hairs. The spermatozoids contain an anterior multilayered structure (MLS) structurally similar to, though smaller than, the MLS observed in zoospores. An asymmetrical cytoskeleton consisting of a band of 30–45 microtubules extends from the MLS down one side of the spermatozoid close to the plasmalemma. An immature MLS was observed in an early stage of spermatozoid development. The finding of an MLS and asymmetrical cytoskeleton in specialized male gametes as well as relatively unspecialized zoospores ofColeochaetestrengthens assumptions of homology between MLSs of green algal reproductive cells and those found in flagellated spermatozoids of archegoniate plants. The structure of the spermatozoid ofColeochaetesupports the hypothesis that this alga may be relatively close to the phylogenetic line which led directly to archegoniates.
DEVELOPMENT OF VACUOLES AND LIPID BODIES IN APICAL MERISTEMS OF PINUS BANKSIANA
Authors: Cecich Robert A.
Published: January 2018

Shoot apical meristems of jack pine were examined weekly during the first 8 weeks post‐germination with light and electron microscopy. Most of the storage lipids were utilized by the end of the 2nd week. A few lipid bodies, possibly high in phospholipid content, remained in the apical initials and central mother cells and, during the 3rd week, gave rise to vacuoles via lamellar or myelin‐like structures which were first seen on their periphery. The inter‐lamellar spaces enlarged and eventually a vacuole was formed. At 5 weeks, elongate and spherical osmiophilic inclusions, presumably lipid, were found in the endoplasmic reticulum. Lipid bodies, visible with light microscopy, began to accumulate in the apical initials and central mother cells in the 6th week.
EPIDERMAL CHARACTERISTICS OF THE CALLUS IN ERIOCHLOA (POACEAE)
Authors: Shaw R. B. , Smeins F. E.
Published: January 2018

A callus or cup at the spikelet base in Eriochloa is a diagnostic character for this genus. In an investigation of Eriochloa and related genera, the callus epidermis of 19 taxa of Eriochloa and the basal portion of Axonopus, Brachiaria, Digitaria, Leptoloma, and Panicum spikelets were examined with a scanning electron microscope. Eriochloa taxa were divided into three types based on callus epidermal characteristics. The callus of E. polystachya more closely resembled the reduced first glume in other panicoid genera than the callus in other taxa of Eriochloa. Bicellular microhairs, silica bodies, and interlocking long cells support the concept that the callus in Eriochloa is in part a remnant of the first glume.
STEM‐ROOT TRANSITION OF AN UPPER PENNSYLVANIAN WOODY LYCOPSID
Authors: Pigg Kathleen B. , Rothwell Gar W.
Published: January 2018

Anatomically preserved specimens of a woody lycopsid showing the transition from the stem to the rooting region are described from the Upper Pennsylvanian Duquesne Coal of Ohio. Specimens have exarch protosteles that are apparently medullated at distal levels and exhibit abundant secondary xylem. Cortical tissues accompanying the stems have periderm, and show leaf bases or cushions. Although features of the stems are compatible with those of the arborescent Lepidodendrales, the plants have a rounded cormose rooting region, rather than the much‐branched and elongated stigmarian system usually associated with the order. Specimens of this type expand our knowledge of the diversity among Paleozoic lycopsids and document the occurrence of representatives with an Isoetes‐like base in Pennsylvanian strata.
ULTRASTRUCTURE OF DEVELOPING SIEVE ELEMENTS IN THLASPI ARVENSE L. I. THE IMMATURE STATE
Authors: Hoefert Lynn L.
Published: January 2018

Immature sieve elements of pennycress (Thlaspi arvense, Brassicaceae) were studied with the electron microscope in connection with studies on virus‐infected plants. Immature sieve elements contained cytoplasm rich in organelles and other components: endoplasmic reticulum, dictyosomes and associated smooth and coated vesicles, mitochondria, plastids, ribosomes, microtubules, microfilaments, vacuoles, and nuclei that were sometimes lobed. Tubular P‐protein (phloem protein) and one to three granular P‐protein bodies also were present in the cytoplasm. Coated vesicles may be involved in formation of the granular P‐protein body and in some aspect of cell wall development, for in the latter case, they were often seen united with the plasmalemma. The association of coated vesicles with the P‐protein body is discussed with reference to proposed concepts of the origin and function of these vesicles.
INFLUENCE OF INSTANTANEOUS AND INTEGRATED LIGHT‐FLUX DENSITY ON LEAF ANATOMY AND PHOTOSYNTHESIS
Authors: Chabot Brian F. , Jurik Thomas W. , Chabot Jean F.
Published: January 2018

Experiments were conducted to examine whether leaf adaptation to light in Fragaria virginiana (Rosaceae) was determined by peak photon‐flux density or by total quanta received during the day. Leaf structure and apparent photosynthesis rates were similar under environments where total energy received was the same even though peak photon‐flux density was different. When peak photon‐flux density was held constant and total quanta varied, significant differences were noted in apparent photosynthesis, leaf thickness, specific leaf weight, mesophyll cell volume, and Ames/A ratio. High total quanta produced high‐light or sun‐type leaves even at relatively low peak intensities. Thus, total light energy received during the day has a greater influence on leaf adaptation to light than does peak photon‐flux density.
DIURNAL VARIATION IN THE TERPENOIDS OF JUNIPERUS SCOPULORUM (CUPRESSACEAE)—SUMMER VERSUS WINTER
Authors: Adams Robert P.
Published: January 2018

Samples of Juniperus scopulorum taken in January, 1977, were compared to samples of July, 1975. Only one significant difference was found in the winter sample compared to thirteen in the summer, 1975 sample. Five compounds showed significant changes from day to day in the winter compared to eleven in the summer. Thirty‐two compounds showed significant differences among trees in the winter in contrast to thirty‐six significant differences in the summer. Diurnal variation can apparently be minimized by sampling during the most dormant period and is strongly encouraged for chemosystematic studies.
CHROMOSOMES OF OREITHALES (RANUNCULACEAE)
Authors: Duncan Thomas , Perez Paul
Published: January 2018

A chromosome count of 2n =48 is reported for Oreithales integrifolia from Peru. This represents the first chromosome report for this genus. This chromosome report is discussed in relation to other genera in the Ranunculaceae.
PRODUCTION OF ANOMALOUS STRUCTURES IN QUERCUS RUBRA L. CALLUS CULTURES
Authors: Seckinger Gary R. , McCown Brent H. , Struckmeyer B. Esther
Published: January 2018

Internodal stem segments of 2–4‐month‐old Quercus rubra L. seedlings were cultured on Murashige and Skoog agar medium containing NAA and BA. Structures, termed organoids, were initiated from callus on medium containing 5 mg/1 NAA and 0.1 mg/1 BA. Organoids consisted of parenchymatous cells with a distinct epidermis and a continuous vascular system. Growth occurred principally by cell division throughout the parenchymatous tissue resulting in a variety of morphological shapes. Although no organized shoot meristems were observed, normal roots were produced; such roots were connected to the vascular system of the organoid.
DEVELOPMENT OF APOGAMIC AMOEBAE FROM HETEROTHALLIC LINES OF A MYXOMYCETE, DIDYMIUM IRIDIS
Authors: Mulleavy Perry , Collins O'Neil Ray
Published: January 2018

By making appropriate crosses between heterothallic sexual clones of Didymium iridis we can recover apogamic lines in the F1 generation. In this organism, heterothallic forms typically produce a haploid myxamoebal stage, but recently two diploid myxamoebal clones homozygous for mating types were discovered. When these are crossed, A2A2 x A5A5, tetraploid Plasmodia are produced which later yield diploid F1 meiospores. Sixty‐four percent of the single‐spore‐derived clones produce both myxamoebae and Plasmodia, while the remainder do not progress past the myxamoebal stage. These results are consistent with the predictions that from tetraploid nuclei, mating types should segregate in the meiospores in a ratio of 1A2A2:4A2A5:1A5A5, and that myxamoebae heterozygous, A2A5, for mating type should yield Plasmodia apogamously. As the means for verifying relative ploidy levels of myxamoebae and Plasmodia, nuclear DNA was measured with a scanning microspectrophotometer.
NIACIN BIOSYNTHESIS IN PLANTS
Authors: Arditti Joseph , Tarr John B.
Published: January 2018

A review of the literature on niacin biosynthesis in plants generally and angiosperms in particular reveals that the available evidence does not conclusively favor or exclude any of the known pathways.
STUDIES IN THE EMBRYOLOGY OF COMPOSITAE. IV. THE TRIBE INULEAE
Authors: Pullaiah T.
Published: January 2018

Embryology of Blumea malabarica, B. membranacea, Laggera pterodonta, Anaphalis busna and Vicoa auriculata has been studied. The anther is tetrasporangiate in all the members except in Blumea membranacea where it is bisporangiate. The anther tapetum is of the Periplasmodial type. Both tetrahedral and isobilateral pollen tetrads are found. Mature pollen grains are three‐celled with thick spinous exine. The ovary is bicarpellary syncarpous and unilocular with a single basal ovule. In one instance in Blumea malabarica two ovules per ovary with a rudimentary septum separating them was observed. The single hypodermal archesporial cell functions directly as the megaspore mother cell. The embryo sac develops according to the Polygonum type. The synergids in Blumea malabarica are hooked while in other members they are pear shaped. There are three antipodal cells except in Blumea membranacea where they increase up to eight. Endosperm development in Blumea malabarica is of the Nuclear type while in Blumea membranacea and Laggera pterodonta it is of the Cellular type. One or two layers of endosperm persist up to maturity. Embryo development follows the Senecio variation of Asterad type. The embryological information of this tribe along with that of other tribes will be utilized in evaluating the interrelationships of the family Compositae in a later paper.
GAMETOPHYTE OF LYCOPODIUM DIGITATUM
Authors: Bruce James G.
Published: January 2018

Gametophytes of Lycopodium digitatum A. Braun are subterranean, mycorrhizal structures. Externally, they are conical and divided into three principal regions: tapering base, ring meristem, and gametangial cap. Internally, the endobiont is restricted to specialized tissues in the base. Gametangia typical of those described for L. complanatum are found along the cap margin near the ring meristem. Comparative analysis of these and other related gametophytes leads to the conclusion that Bruchmann's Type I (L. clavatum) and Type II (L. complanatum) gametophytes cannot be consistently separated on the basis of 1) mycorrhizal tissues, 2) form of gametophyte, and 3) number of neck canal cells in the archegonium, as he had proposed. Consequently, it is suggested on the basis of ring meristem and radial symmetry, mycorrhizal tissue specialization, and lack of sterile paraphyses or lobes that Type I and Type II gametophytes be merged as a single type. The now broadened clavatumcomplanatum type is restricted to subgenus Lycopodium (sensu Wilce) where it is the only known type.
GAMETOPHYTE AND YOUNG SPOROPHYTE OF LYCOPODIUM CAROLINIANUM
Authors: Bruce James G.
Published: January 2018

Gametophytes of Lycopodium carolinianum L. are green and superficial. Rhizoids invest the lower surface of the dorsiventral axes, multicellular lobes, the upper surface. Growth is apical. Gametangia occur mixed and always between lobes or around the lobe bases. Embryogeny is abbreviated with no protocorm. Following protophyll emergence, the rhizome apex forms laterally and the first root is initiated. Development of dorsal leaves, characteristic of adult rhizomes, is delayed until after the second pair of lateral leaves has formed. Features of the gametophyte and embryonic stages of the sporophyte provide additional comparative evidence supporting the view that L. carolinianum arose from along the phylogenetic line leading from subgenus Lepidotis to subgenus Lycopodium.
EVOLUTIONARY STUDIES OF ATRIPLEX: ADAPTIVE PRODUCTS FROM THE NATURAL HYBRID, 6N A. TRIDENTATA x 4N A. CANESCENS
Authors: Stutz Howard C. , Pope C. Lorenzo , Sanderson Stewart C.
Published: January 2018

Much of the variation in hexaploid Atriplex tridentata appears to have come from tetraploid A. canescens by introgression. Among the recombinations, three types appear to have become established as new, adaptive, hexaploid derivatives. One of these is a robust, woody form near Knolls, Utah, another is a widespread, low‐growing, shrubby form in Lander County, Nevada, the other is an upright bushy, canescens‐like form near Grantsville, Utah.
INVESTIGATIONS OF ANGIOSPERMS FROM THE EOCENE OF NORTH AMERICA: STIPULATE LEAVES OF THE RUBIACEAE INCLUDING A PROBABLE POLYPLOID POPULATION
Authors: Roth John L. , Dilcher David L.
Published: January 2018

A comparative study was made of the gross morphology, fine venation and cuticular features of Leitneria fioridana Chapman, the single living representative of the order Leitneriales and Leitneria eocenica (Berry) Brown, presumbaly a related fossil species. In addition to the type material, newly collected fossil specimens were investigated from clay pits in the Middle Eocene, Claiborne Formation, of western Tennessee and Kentucky. Foliate stipules attached to the petioles of several specimens suggest the assignment of this fossil leaf type to the genus Leitneria is incorrect. The nature of the gross morphology, fine venation and cuticular features confirms the misidentification. Previously, various specimens of this fossil leaf type have been placed in eight species of seven genera in seven families of six angiosperm orders, none of which are correct systematically. The gross morphology, venation and cuticular characters of the fossil leaf are distributed among a few extant South American genera of arborescent Rubiaceae. The fossil is an extinct rubiaceous leaf type which cannot be placed within a single modern subfamily, tribe or genus of the family. The organ genus, Paleorubiaceophyllum is proposed for these leaves. Three varieties of a single fossil species, P. eocenicum, are recognized. One variety with epidermal cells nearly twice the size of the others may represent a polyploid population.
VACUOLE FORMATION IN THE ACTIVELY GROWING ROOT MERISTEM OF BARLEY (HORDEUM SATIVUM)
Authors: Buvat Roger , Robert Ginette
Published: January 2018

The subapical meristem of actively growing barley roots produces series of undifferentiated cells, some of which are devoid of vacuoles. At the beginning of their differentiation, the Golgi apparatus gives rise to vesicles and tubules which concentrate hydrolases, acid phosphatase being the typical representative of these enzymes. Some of these structures organize themselves as sequestration vacuoles. Then, the imprisoned fraction is destroyed by the process of autophagy after an alteration of the vacuolar internal membrane. These structures are identical to the “provacuolar apparatus” described by Marty in Euphorbia characias roots. Lytic processes which develop in autophagic vacuoles give rise to the first true meristematic vacuoles. Relations between dictyosomes, provacuoles and vacuoles, and their degree of exclusivity are discussed.
SPORE MORPHOLOGY IN THE CYATHEACEAE. III. THE GENUS TRICHIPTERIS
Authors: Gastony Gerald J.
Published: January 2018

Scanning electron microscopy supported by light microscopic L‐O analysis is used in a palynological study of the genus Trichipteris of the tree fern family Cyatheaceae. The spores of all but two of the 55 species are investigated and the results are related to previous findings for Trichipteris species in the literature. A perine layer consisting of a network of slender, smooth‐ or rough‐textured interlocking strands with free ends uniformly characterizes the genus and is the same as the perine type previously reported in neotropical species of Sphaeropteris excluding the S. horrida group. The exine is analyzed both in spores which have not yet developed the perine layer and in spores whose perine has been removed by chemical treatment. Exine sculpturing shows great variation in the genus, ranging from essentially psilate to variously pitted (foveolate, foraminate), with topography ranging from plane to verrucate‐tuberculate, and with the verrucae‐tubercles themselves often variously pitted. In many instances, exine sculpturing types correlate with the infrageneric species groupings or affinities hypothesized by the recent monographers. In other cases, palynological characters offer new insight into species relationships that were previously unclear to monographers or that were interpreted differently on the basis of other characters. The exine sculpturing types reinforce the relationship evident between Trichipteris and neotropical Sphaeropteris on the basis of perine morphology.
TENSIONAL STRESS IN THE CAMBIUM AND ITS DEVELOPMENTAL SIGNIFICANCE
Authors: Hejnowicz Z.
Published: January 2018

In the mitotically active vascular cambium of conifers and broadleaved trees there is tension across the radial middle lamellae. This tension seems to be important for intrusive growth of fusiform cells. In the vascular cambium of Fraxinus and Robinia there is tension across the tangential middle lamellae also, which makes possible the increase in diameter of differentiating vessel members.
ENDOMYCORRHIZAE INFLUENCE GROWTH OF BLACKGUM SEEDLINGS IN FLOODED SOILS
Authors: Keeley Jon E.
Published: January 2018

Nyssa sylvatica seedlings grown for a year under flooded conditions established endomycorrhizal associations with Glomus mosseae. Lowland ecotypes with endomycorrhizae showed a significant increase in biomass over non‐mycorrhizal controls; the greatest difference was in aboveground biomass. Upland ecotypes survived flooding poorly and established fewer endomycorrhizae than lowland ecotypes and did not show any enhanced growth over controls. In general, most endomycorrhizae were formed near main roots and significantly decreased in abundance with distance from the main axes of the root system. It is suggested that under flooded conditions internal oxygen transport may be limiting to mycorrhizae in the more distal roots.
NUTRIENT CHANGES IN TWO CHAPARRAL SHRUBS ALONG A FIRE‐INDUCED AGE GRADIENT
Authors: Rundel Philip W. , Parsons David J.
Published: January 2018

Adenostoma fasciculatum H. & A. and Ceanothus leucodermis Green in chaparral stands of the foothill zone of Sequoia National Park, California, show a rapid decline in foliage concentrations of nitrogen over the first six years following fire. This is followed by a more gradual decline over succeeding years. Phosphorus concentrations show a similar early decline, followed by an increase in older age stands. Considerable data suggest luxury consumption of nutrients in both species following fire. Following a sharp increase in aboveground nutrients per unit of Adenostoma canopy area for the first 16 years of growth, a plateau is reached. The contemporaneous occurrence of restricted net nutrient uptake and observed stand senescence suggest a possibility of a causal relationship. Natural chaparral fire frequencies promote fire‐cycling of nutrients at intervals consistent with periods when nutrient availability becomes limiting. The fire‐nutrient interactions are of critical importance in influencing quality and quantity of suitable browse for vertebrate herbivores.
HETEROSTYLY, POPULATION COMPOSITION, AND POLLEN FLOW IN HEDYOTIS CAERULEA
Authors: Ornduff Robert
Published: January 2018

Hedyotis caerulea is a perennial, spring‐flowering herb native to eastern North America with distylous flowers that differ in a number of morphological and physiological traits. However, the pin and thrum morphs produce the same numbers of buds, flowers, and fruits per plant, although it is possible that differences in these may occur in some populations at certain times of the flowering period. The two morphs are self‐incompatible and cross‐compatible. Most populations contained an excess of pins over thrums (anisoplethy); less commonly pins and thrums were equally represented (isoplethy). Populations change from anisoplethy to isoplethy and in the reverse direction. The spatial distribution of pin and thrum flowers in populations was random in some populations but non‐random in others. There is some indication that the two morphs in some populations have somewhat different flowering periods. Pollinators seem to be chiefly bombyliid flies and perhaps thrips, but insects were rarely observed visiting flowers. In some populations, the two morphs produced equal numbers of pollen grains per flower; in others they did not. The average pollen viability varied, but on the average there was a moderate level of pollen sterility. High numbers of pollen grains remained in dehisced anthers, probably as a result of low pollinator activity. However, between 5% and 9% of the pollen produced participated in pollination. Stigmas of most pin flowers received more pin pollen grains than thrum pollen grains; on stigmas of thrum flowers pin pollen grains outnumbered thrum pollen grains. Thus, compatible pollen flow from pins to thrums was greater than in the reverse direction. Anisoplethic and isoplethic populations had the same pollen flow patterns. A plant‐by‐plant examination of stigmas indicated that many stigmas bore few or no pollen grains. Seed production of the two morphs was equal. Despite the inequities in pollen flow patterns, the widespread and occasionally weedy nature of H. caerulea suggests that its breeding system must be viewed as a successful one.
DEVELOPMENT OF CHAMBERED PITH IN STEMS OF PHYTOLACCA AMERICANA L. (PHYTOLACCACEAE)
Authors: Mikesell Jan E. , Schroeder Allen C.
Published: January 2018

An integrated microscopic (light and electron microscopy) and macroscopic investigation of chambered pith development was made of Phytolacca americana L. Terminal internodes have a solid pith cylinder in contrast to the alternating diaphragms and chambers occurring in subjacent pith. Macroscopically, chambers and diaphragms of any one internode are of equal size. Microscopically, diaphragms vary in height within an internode (from 1–6 cells high). Nevertheless, all diaphragms become thicker circumferentially (5–12 cells high) and connect with long files of intact peripheral pith cells. Diaphragm cells have a large centrally positioned vacuole with a thin, parietal layer of cytoplasm; nuclei, mitochondria, endoplasmic reticulum, and unidentified organelles differentiate in the cytoplasm of diaphragm cells. Although schizogenous activity has most often been implicated as the mechanism by which chambered pith develops in vegetative organs of angiosperms, the results of this study show that cavities in pokeweed result from both schizogenous and lysigenous mechanisms. Schizogeny is suggested by the fact that central pith cells of terminal internodes are longer and thinner walled than peripheral pith cells arranged in vertical files, thus indicating elongation of cells as a possible result of internode elongation. The precise developmental pattern and arrangement of chambers and diaphragms also suggest schizogenous processes. Lysigenous or enzymatic activity is indicated by the fact that cavities are bounded by broken cells, and wall fragments and organelles are often found within enlarging cavities. Chamber formation occurs continuously acropetally and centrifugally in the central pith. A comparison of diaphragms is made with Liriodendron tulipifera and Juglans nigra in an attempt to resolve differences in structure and terminology regarding the differentiation of chambered and diaphragmed pith.
DEVELOPMENTAL CHANGES IN THE ALGAL COENOCYTE CAULERPA PROLIFERA (SIPHONALES) AFTER INVERSION WITH RESPECT TO GRAVITY
Authors: Jacobs Wm. P. , Olson Jana
Published: January 2018

The algal coenocyte Caulerpa prolifera produces three types of organs, each with a different orientation. The effect of gravity in controlling the development of these organs was investigated. We inverted plants by rotating them 180° around the horizontal rhizome axis, then compared development of the inverted plants with plants matched by size and differentiation. Quantitative data were obtained from photographic records. After inversion the site of organ differentiation was changed with no change in the timing: the next rhizoid (and all subsequent ones) differentiated on the “now‐under side” of the inverted rhizome, the next leaf formed on the “now‐upper side.” Despite the fast change in the site of organ differentiation, other parameters were not changed by inversion (e.g., rate of elongation of rhizomes or leaves, rate of formation of leaves or rhizoids). Because such changes also occurred in plants with balanced lighting from two sides, it is clear that gravity alone can control these changes without reinforcement from top illumination. After leaves were initiated, they did not change their orientation, showing neither positive phototropism (at our light levels) nor negative geotropism, even when elongating substantially. Torsion of the rhizome tip did not precede the change in site of rhizoid initiation.