bluuebunny/crossref_metadata_2025 huggingface dataset:
EARLY HISTOGENESIS AND SEMIQUANTITATIVE HISTOCHEMISTRY OF LEAF INITIATION IN TRITICUM AESTIVUM
Authors: Evans Lance S. , Berg Arthur R.
Published: January 2018

The shoot apex of Triticum aestivum cv. Ramona 50 was investigated histologically to describe cell lineages and events during leaf initiation. During histogenesis three periclinal divisions occurred in the first apical layer, with one or two divisions in the second apical layer. This sequence of cell divisions initially occurred in one region and spread laterally in both directions to encircle the meristem. Cells of the third apical layer were not involved in leaf histogenesis. Initially, young leaf primordia were produced from daughter cells of periclinal divisions in the two outer apical layers. Nuclear contents of protein, histone, and RNA in the shoot apex were evaluated as ratios to DNA by means of semiquantitative histochemistry. Daughter cells of periclinal divisions in the outer apical layer which produced the leaf primordia had higher histone/DNA ratios than cells of the remaining meristem. However, protein/DNA and RNA/DNA ratios were similar in both regions. Leaf initial cells had a higher 3H‐thymidine labeling index, a higher RNA synthesis rate, and smaller nuclear volumes than cells of the residual apical meristem.
PHYSIOLOGICAL ECOLOGY OF GERMINATION OF VIOLA RAFINESQUII
Authors: Baskin Jerry M. , Baskin Carol C.
Published: January 2018

Seeds of the winter annual Viola rafinesquii Greene exhibit true dormancy at the time of maturity and dispersal in mid to late spring. During the summer rest period the seeds pass from a state of true dormancy to one of relative dormancy and finally to what may be called a state of complete nondormancy. As the seeds enter relative dormancy they will germinate mostly at relatively low temperatures (10, 15, 15/6, and 20/10 C), but as after‐ripening continues they gain the ability also to germinate at higher temperatures (20, 25, and 30/15 C). During June, July, and August seeds will not germinate at field temperatures even if kept continuously moist. But by September and October seeds may germinate to high percentages over a wide range of temperatures, including September and October field temperatures. This pattern of germination responses, involving breaking of true dormancy and widening of the temperature range for germination during relative dormancy, appears to be an adaptation of the species to a hot, dry season. Seeds of V. rafinesquii stored on continuously wet soil (field capacity) or on soil that was alternately wet and dried during the summer did not after‐ripen at low temperatures (10, 15, 15/6, and 20/10 C) but did after‐ripen fully at high temperatures (20, 25, 30/15, and 35/20 C). Thus, the high temperatures that V. rafinesquii “avoids” by passing the summer in the dormant seed stage actually are required to break seed dormancy and, therefore, are essential for completion of its life cycle.
POLLEN ORGANS OF THE PENNSYLVANIAN CALLISTOPHYTACEAE (PTERIDOSPERMOPSIDA)
Authors: Rothwell Gar W.
Published: January 2018

Numerous specimens of the pteridospermous pollen organs Idanothekion glandulosum and Callandrium callistophytoides are present in Middle and Upper Pennsylvanian petrifaction material, respectively. Several specimens of Idanothekion, previously known only in an isolated condition, are attached to foliage assignable to the monostelic seed fern Callistophyton. Proof of the affinities of Idanothekion allows this genus to be elevated from a form genus to an organ genus in the Callistophytaceae. The structure of the foliage and the mode of attachment of the Idanothekion specimens are like those previously described for Callandrium. Structural features of Idanothekion and Callandrium are compared, and the question of their identity is discussed. At present one basic type of pollen organ, borne on the abaxial surface of foliar pinnules, is known for members of the Callistophytaceae.
CONTROL OF SHOOT‐RHIZOME DIMORPHISM IN THE WOODY MONOCOTYLEDON, CORDYLINE (AGAVACEAE)
Authors: Fisher Jack B.
Published: January 2018

In Cordyline terminalis negatively geotropic leafy shoots and positively geotropic rhizomes develop from single axillary buds on either shoots or rhizomes. All axillary buds have similar morphogenetic potential when released from apical dominance. Experiments in which the orientation of the apex is changed, organs removed, or growth regulators applied indicate that after a rhizome is initiated, it is maintained as a rhizome by auxin originating in the leafy shoot. When auxin levels are lowered by changes in the orientation of the axis or shoot removal, the rhizome apex becomes a shoot apex, which appears to be the stable state of the actively growing apex. Benzyl adenine when applied exogenously to the apex or lateral buds has the same effect as lowering the auxin level. Gibberellic acid has no effect on the apex or lateral buds. High levels of exogenous naphthaleneacetic acid cause bud release and development of rhizomes from previously inhibited axillary buds of the shoot. However, it was not possible to convert a shoot apex into a rhizome apex by auxin treatment. It is suggested that the release of buds on the lower side of horizontal branches and of buds directly above a stem girdle is caused by high auxin levels on the lower side or distal to the girdle. The experimental results are discussed in relation to naturally occurring shoot‐rhizome dimorphism.
AN ULTRASTRUCTURAL STUDY OF FERN GAMETOPHYTES DURING ONE‐ TO TWO‐DIMENSIONAL DEVELOPMENT
Authors: Stetler D. A. , DeMaggio A. E.
Published: January 2018

During early stages in the transition from 1‐ to 2‐dimensional gametophyte development the change from filamentous to bulbous apical cell is not accompanied by major changes in the nature or number of cytoplasmic components of the cell. However, chloroplasts in apical cells of plants grown in red light are larger than those from cells of plants grown in blue light. In addition, the orientation of cytoplasmic microtubules is different in apical cells of plants from red and blue light. This change in orientation may be causally related to the change in apical cell form during 1‐ to 2‐dimensional growth.
CYTOLOGY OF MAIZE‐TRIPSACUM INTROGRESSION
Authors: de Wet J. M. J. , Engle L. M. , Grant C. A. , Tanaka S. T.
Published: January 2018

The American Maydinae genera Zea and Tripsacum cross readily when not isolated from each other by gametophytic barriers, and it has been suggested that intergeneric introgression played a role in the evolution of maize. Four Zea chromosomes pair with members of at least one basic genome of tetraploid Tripsacum, and in hybrids involving octaploid Tripsacum all 10 chromosomes of the basic maize genome frequently compete successfully in synapsis with Tripsacum chromosomes. Hybrids that combine 36 Tripsacum and 10 maize chromosomes are female fertile. When they are pollinated by maize their offspring have 36 Tripsacum and 20 maize chromosomes, or again have 36 Tripsacum and 10 maize chromosomes, but the 10 Zea chromosomes are contributed by the new pollen parent. Later backcross generations also include plants with 36 Tripsacum and 12, 14, 16, or 18 maize chromosomes. Individuals with 2n = 56 produce an abundance of offspring with 18 Tripsacum and 20 maize chromosomes when backcrossed with maize. Further backcrossing results in elimination of Tripsacum chromosomes, and eventually plants with 2n = 20 Tripsacum‐contaminated maize chromosomes are obtained. Two generations of selfing restore full fertility to these 2n = 20 plants and eliminate all obvious traces of Tripsacum morphology.
THE SUGARS OF SOME FLORIDA NECTARS
Authors: Van Handel E. , Haeger J. S. , Hansen C. W.
Published: January 2018

The quantitative composition of major sugars in the nectars of 35 plant species was compared with that of 12 fruit juices. The use of specific quantitative assays for glucose, fructose, and sucrose made it possible to analyze large samples without quantitative chromatographic separations. Sucrose ranged from 0–99%. In most nectars, glucose and fructose were present in approximately equal amounts. No evidence was found for the presence of maltose, raffinose, and other oligosaccharides.
CULTURAL CHARACTERS IN RAMARIA SUBG. LENTORAMARIA, AND A NEW TAXON
Authors: Petersen Ronald H.
Published: January 2018

Cultural characters for Ramaria apiculata var. apiculata, R. acris, R. gracilis, and R. stricta var. concolor are described. Ramaria apiculata var. brunnea, var. nov. is proposed and its fruit bodies and cultural characters described.
INVESTIGATIONS OF NORTH AMERICAN CYCADEOIDS: POLLINATION MECHANISMS IN CYCADEOIDEA
Authors: Crepet William L.
Published: January 2018

Wind was at first thought of as the chief pollinating mechanism in Cycadeoidea because of the open angiosperm‐flower‐like reconstruction of the cone presented by G. R. Wieland in 1906. Selfing seemed a more likely possibility after Delevoryas reinterpreted the cone as a closed structure in 1963. However, the existence of what was considered to be a dioecious group of species made it impossible to consider selfing as ubiquitous throughout the cycadeoids. Furthermore, only ovule‐bearing trunks of the species considered to be dioecious were known; no corresponding trunks bearing exclusively microsporangiate cones had ever been found. Recent investigations of a trunk of the type heretofore considered as representative of the dioecious species have revealed that these cones were actually bisporangiate. The discovery that the bisporangiate condition was normal in the cycadeoids eliminates much of the confusion in understanding the system of pollination and allows selfing to be considered the chief means of pollination. Outcrossing probably occurred in very low frequency and could have been the result of a chance wind pollination or of a set of interactions between the cycadeoids and an unidentified animal. Determining the nature of the system of pollination in the cycadeoids makes it possible to speculate on the population structure and evolutionary potential of this important Mesozoic group of plants.
PHOTOMORPHOGENESIS OF THE GAMETOPHYTES OF LYGODIUM JAPONICUM
Authors: Raghavan V.
Published: January 2018

Protonemata of Lygodium japonicum turn biplanar in both red and blue light regimes and remain filamentous in far‐red light. Biplanar gametophytes formed in red light are longer than broad with long, rectangular cells, whereas in blue light they appear broader than long with short, isodiametric cells. Transfer of protonemata of all ages from far‐red regime to red or blue light induces a morphological type of growth characteristic of the new light regime. However, only relatively young biplanar forms transferred from red or blue light are able to resume filamentous type of growth in a subsequent regime of far‐red light.
NUTRITIONAL REQUIREMENTS FOR OVULE FORMATION IN EXCISED PISTILS OF NIGELLA
Authors: Peterson Curt M.
Published: January 2018

The nutritional requirements for ovule formation in Nigella saliva L. were investigated by growing excised pistils on defined media. Pistils grown on a medium containing the minerals of Murashige and Skoog produced significantly more ovules than on a medium containing the minerals of Bilderback. When the nitrogen, sulfate, and phosphate of the Bilderback medium were adjusted to levels comparable to those of the Murashige and Skoog medium, a similar number of ovules was formed. The effect of different forms and concentrations of nitrogen on ovule formation and pistil growth was investigated. High concentrations of nitrate (40 mil) favored pistil growth and ovule formation, but comparable levels of ammonium were toxic. When ammonium at concentrations above 10 mM was added to nitrate media, ovule formation was inhibited. A medium containing low concentrations of ammonium (10 mM) and nitrate (5 mM) supported more ovule formation and pistil growth in young pistils than a low‐nitrate (5 mM) medium without ammonium. However, ovule formation on a medium containing 10 mM ammonium and 5 mM nitrate was significantly less than on a medium containing only 15 mM nitrate. Low concentrations of organic nitrogen in the form of α‐alanine (1 mM) and γ‐aminobutyric acid (5 mM) supported ovule formation and pistil growth similar to a high nitrate medium.
PHYLLODE THEORY IN RELATION TO LEAF ONTOGENY IN SANSEVIERIA TRIFASCIATA
Authors: Stevenson Dennis Wm.
Published: January 2018

Shoot apices of Sansevieria trifasciata have a three‐layered mantle, a zone of subapical initials, a central meristem, and a peripheral meristem. Leaf initiation begins with periclinal divisions in L‐3 and is followed by periclinal divisions in L‐2 and anticlinal divisions in L‐l. At first, the primordium is a mound of tissue at one point on the flank, but it soon takes the form of a low ridge encircling the apex. An ephemeral adaxial meristem differentiates in L‐2 of the primordium when it is about 50 μ high and is active until the primordium is about 450 μ high. Then it ceases basipetally and is not observable after the primordium is about 600μ high. As the adaxial meristem ceases at the base of the radial tip, its two lateral regions become the submarginal meristems of the expanded portion. Marginal meristems differentiate from the protoderm, and oblique‐anticlinal divisions of the marginal initials result in the formation of an abaxial and adaxial epidermis. These derivatives undergo a few anticlinal divisions, increasing marginal width, and then they divide periclinally, increasing marginal thickness. After the primordium is about 600‐700 μ high it continues to grow in length by a diffuse basal intercalary meristem. When the leaf is 3 dm long, an adaxial rounding meristem differentiates in the region just above the sheath. Leaf vasculature consists of parallel bundles which anastomose acropetally. Vascular bundles are arranged in a semicircle in the expanded portion and in a circle in the radial tip. There is one centrally located bundle at the apex as a result of lateral anastomoses. Present evidence from leaf ontogeny and mature vasculature in S. trifasciata is interpreted as supporting the concept that the liliaceous leaf is homologous with the phyllodes of A corns and Acacia.
PHOTOPERIODIC ADAPTATION IN DESERT POPULATIONS OF XANTHIUM STRUMARIUM
Authors: McMillan Calvin
Published: January 2018

Reproductive adaptation to photoperiod is diverse among desert populations of Xanthium. Chihuahuan Desert populations require dark periods of 9.5–10.5 hr for reproduction, and Sonoran Desert populations require 9–10.5 hr. Many Chihuahuan populations from western Texas two weeks from sowing need only 10 cycles of 11‐hr nights to produce 100% flowering, but Sonoran populations from western Mexico four weeks from sowing need 18 cycles or more. Some Sonoran plants produce buds only at a cooler temperature program, 24–15 C, but Chihuahuan plants produce them more readily under the warmer program, 30–24 C. Chihuahuan plants that were germinated under 11‐hr nights and four different temperature programs were induced to flower in each condition. Differences in photoperiod and ripeness‐to‐flower (maturity) responses were also demonstrated under natural day lengths in central Texas. Although desert populations occurring at approximately the same latitude in either the Chihuahuan or Sonoran Desert are exposed to similar day lengths, each population may be adapted to different photoperiod cues that maximize its utilization of the local growing conditions.
THE MORPHOLOGY OF STIGMARIA STELLATA
Authors: Jennings James R.
Published: January 2018

Stigmaria stellata Goeppert is a lycopod underground system occurring in Upper Mississippian and equivalent age rocks of Europe and North America. This taxon has previously been based on impressions exhibiting radiating ridges and furrows around each lateral appendage scar and numerous polyhedral projections on the remainder of the axis. Anatomically preserved specimens from the Chester Series (Upper Mississippian) of Illinois reveal that the distinctive surface pattern of this species results from polyhedral wedges of thick‐walled cells in the outer cortex. Decortication produces a smooth outer surface that is indistinguishable from that of the much more abundant Stigmaria ficoides. The structure of S. stellata is quite similar to the structure of other petrified stigmarians, but the following are some of the anatomical characters that distinguish it: (1) presence of abundant polyhedral wedges of thick‐walled cells in the outer cortex; (2) absence of secondary cortex; (3) very tall rays associated with appendage traces that remain confluent with the secondary xylem to its outer margin; (4) the absence of a connective in the lateral appendages. The anatomical characters of Stigmaria stellata confirm it as a taxon of at least specific rank.
SEASONAL PATTERN OF NET PHOTOSYNTHESIS OF ARTEMISIA TRIDENTATA
Authors: DePuit Edward J. , Caldwell Martyn M.
Published: January 2018

Gas exchange studies were carried out on Artemisia tridentata during the course of a growing season using microclimatically controlled cuvettes and infrared gas analysis. A definite seasonal pattern of net photosynthesis emerged. This pattern was influenced by the interaction of four major factors: plant water potential, leaf temperature, irradiation, and stage of phenological development. In spring and early summer, when plant water stress was minimal, photosynthesis rate was mainly correlated with leaf temperature and irradiation. During mid and late summer, increased plant water stress and phenological changes assumed at least equal importance with temperature and irradiation in limiting net photosynthesis. Indeed, plant water potential, mainly through its influence on stomatal aperture, rs‘, was probably the single most important factor influencing assimilation rate of this species on a seasonal basis. However, variations in mesophyll resistance to CO2 flux, rm‘, in response to temperature, water stress, or phenological changes also were involved. Sagebrush photosynthesis under field conditions was highest in late May and early June, and declined thereafter, minimum rates occurring in August during the driest period. Optimal temperatures for net photosynthesis were higher later in the season, indicating a change in gas exchange capacity more suitable to the warmer temperatures later in the season.
THE VEGETATIVE ANATOMY OF SCHOPFIASTRUM DECUSSATUM FROM THE MIDDLE PENNSYLVANIAN OF THE ILLINOIS BASIN
Authors: Stidd Benton M. , Phillips Tom L.
Published: January 2018

Schopfiastrum decussatum, a monostelic pteridosperm, has been recovered from Middle Pennsylvanian age coal balls from six localities within the Illinois Basin. Additional features of stem anatomy include the presence of horizontal sclerotic plates in the inner cortex, secretory ducts in the inner and outer cortex, and adventitious roots. The primary xylem is interpreted as bilobed, emitting massive leaf traces in a distichous manner. Five orders of frond members are described, including pinnules. All orders of the frond contain secretory ducts and tissues characteristic of Schopfiastrum stems. The rectangular, bilobed protostele, and method of leaf trace origin indicate that Schopfiastrum is more closely related to certain lower Carboniferous seed ferns than to contemporary Pennsylvanian pteridosperms.
STUDIES OF PACIFIC ISLAND PLANTS. XXVI. METROSIDEROS COLLINA (MYRTACEAE) AND ITS RELATIVES IN THE SOUTHERN PACIFIC
Authors: Smith Albert C.
Published: January 2018

The genus Metrosideros (Myrtaceae) is an abundant and taxonomically confusing component of the vegetation throughout much of its range. In the southern Pacific, from the New Hebrides eastward to the Society and Tuamotu Islands, the genus is represented by one variable species, M. collina (J. R. & G. Forst.) A. Gray, in which three widespread varieties seem to merit recognition. An attempt is here made to clarify the nomenclature and inter‐relationships of these varieties. Additionally, two local endemics are related to the M. collina group—M. gregoryi Christophersen in Samoa and M. ochrantha A. C. Sm. (sp. nov.) in Fiji.
THE KRANZ SYNDROME IN THE GRAMINEAE AS INDICATED BY CARBON ISOTOPIC RATIOS
Authors: Smith Bruce N. , Brown Walter V.
Published: January 2018

The Kranz syndrome, as indicated by relatively high 13C/12C ratios is characteristic of 16 ½ tribes and about ½ of the species of the Gramineae. Data are given for 198 species from 129 genera and 47 tribes, and from at least 6 subfamilies of grasses. This information is correlated with data from the literature on anatomical and physiological characters of both Kranz and non‐Kranz grasses. All subfamilies, tribes, and genera seem to be uniformly all Kranz or non‐Kranz except the subfamily Panicoideae and the genus Panicum which have both Kranz and non‐Kranz species represented.
MORPHOLOGY OF GLANDULAR HAIRS OF CANNABIS SATIVA FROM SCANNING ELECTRON MICROSCOPY
Authors: Hammond Charles T. , Mahlberg Paul G.
Published: January 2018

Three distinct types of glandular hairs of increasing morphological complexity which occur on flowering tops of Cannabis sativa L. (marihuana) are described from scanning electron microscopy. These gland types—termed bulbous, capitate‐sessile, and capitate‐stalked, described from pistillate plants—occur in greatest abundance on the outer surface of bracts ensheathing the ovary. Bulbous and capitate‐sessile glands, which arise at an early stage in bract development, are scattered over the bract surface. Mature bulbous glands have a small swollen head on a short stalk, whereas capitate‐sessile glands have a large globular head attached directly to the bract surface. Because of their numbers and large size, capitate‐sessile glands are the most conspicuous gland type during the early phase of bract development. Capitate‐stalked glands, which have a large globular head on a tall, multicellular stalk, differentiate during subsequent bract development. These stalked glands arise first along the bracteal veins and then over the entire bract surface. A voluminous, fluid secretory product accumulates in the glandular head of all three types. These glands are believed to be a primary site of localization of the marihuana hallucinogen, tetrahydrocannabinol.
INCORPORATION OF TRITIATED THYMIDINE DURING VARIOUS STAGES OF LEAF DEVELOPMENT OF XANTHIUM PENNSYLVANICUM
Authors: Maksymowych R. , Maksymowych A. B.
Published: January 2018

3H‐thymidine was incorporated into leaf tissue of Xanthium pennsylvanicum during the stage of active cell division, during cellular differentiation, and into mature cells. Incorporation into nuclear DNA was high in the early stages of development. No nuclear incorporation was found after cessation of cell division. However, significant incorporation could be demonstrated in cytoplasm of differentiating and mature cells. Depending upon the time of growth in the radioisotope and the time of growth after treatment, 3H‐thymidine, or its metabolized fraction, was incorporated into the secondary wall depositions of epidermal cells, mesophyll parenchyma cells, xylem cells, and chloroplasts. Autoradiographic technique and liquid scintillation spectrometry were used in these studies. The significance of 3H‐thymidine incorporation into various organelles is discussed in relation to cell metabolism and its regulation during leaf development.
SEXUAL AND SUBSEXUAL SYSTEMS IN HOMOSPOROUS PTERIDOPHYTES: A NEW HYPOTHESIS
Authors: Klekowski Edward J.
Published: January 2018

Meiosis in homosporous ferns allows chromosomes to pair within homoeologous sets rather than restricting pairing to homologs; this allows homozygous spore mother cells to give rise to genetically heterogeneous meiospores. It is envisioned that such a meiotic system has evolved in homosporous ferns in response to a life cycle which allows the attainment of total homozygosity in one generation of selfing.
GENETIC DIFFERENTIATION, SYMPATRIC SPECIATION, AND THE ORIGIN OF A DIPLOID SPECIES OF STEPHANOMERIA
Authors: Gottlieb L. D.
Published: January 2018

Evidence is presented that a geographically peripheral population of the annual Stephanomcria exigua ssp. coronaria (Compositae), a widespread and ecologically diverse species, has recently given rise by a process of sympatric speciation to a diploid species presently designated “Malheurensis.” The new species comprises less than 250 individuals and is found only at a single locality in eastern Oregon where it grows interspersed with its parental population. Stephanomeria exigua ssp. coronaria is an obligate outcrosser and “Malheurensis” is highly self‐pollinating. Reproductive isolation is maintained by differences in breeding system, a crossability barrier that reduces seed set following cross‐pollination between them, and reduction in hybrid fertility caused by chromosomal structural differences. They are very similar morphologically. Electrophoretic analyses of seven enzyme systems demonstrate that all the alleles but one at the controlling 13 gene loci in “Malheurensis” are identical to alleles in ssp. coronaria. The new species displays certain maladapted features including loss of the specific requirements for seed germination characteristic of the progenitor population of ssp. coronaria. The origin of “Malheurensis” appears to be an exception to the theory of geographical speciation because spatial isolation is not necessary at any time for the origin or establishment of its reproductive isolating barriers. The nature of these barriers plus the genetic homogeneity of the species are compatible with the hypothesis that it derives from a single progenitor individual. Very little genetic change is involved initially in this mode of speciation.
WHITE PINE SHOOTS: ROLES OF GRAVITY AND EPINASTY IN MOVEMENTS AND COMPRESSION WOOD LOCATION
Authors: Wilson Brayton F.
Published: January 2018

Pinus strobus L. trees were grown on a clinostat. Although elongating shoots moved in almost the reverse of the normal pattern, they reached a normal original angle. Compression wood (CW) formed only on the upper side of branches opposite where CW had previously formed. Neither treatments to remove epinasty (girdling branches, removing leaders and branches), nor treatments to bend branches out of position changed CW distribution. On trees grown off the clinostat, branches bending upwards after removal of the terminal formed CW on the upper side before reaching vertical. Main stems could form CW on the upper side after having been tipped to induce CW formation on the under side. It is suggested that epinasty is not involved in either early shoot movements or in compression wood location and that when gravity stimulates CW formation on the under side of a shoot it preconditions the upper side for CW formation, thus establishing an equilibrium position for the shoot.
ORGANIZATION AND BREAKDOWN OF THE PROTOPLAST DURING MATURATION OF PINE TRACHEIDS
Authors: Wodzicki Tomasz J. , Brown Claud L.
Published: January 2018

The protoplast of maturing axial tracheids in the secondary xylem of shortleaf pine (Pinus echinata Mill.) was studied by transmission and scanning electron microscopy. The mature protoplast is differentiated into two interconnected components: (1) the commonly observed peripheral layer lining the secondary cell wall, and (2) an elaborate reticulum of cytoplasmic filaments and placoids within the central vacuole. The reticulum provides an extensive surface area of vacuolar membranes for rapid exchange of nutrients and metabolites with the vacuolar sap, which is envisaged to function as a vital medium during the period of secondary cell wall synthesis. The breakdown of the protoplast which terminates tracheid maturation is associated with poorly defined alterations of the vacuolar membranes. This is indicated by increased formation of cytoplasmic spherules and membraneous vesicles which may be portions of separated vacuolar membrane during early stages of degradation. Autolysis is supposed to occur when the cytoplasm is exposed to the vacuolar sap after rupture and separation of the vacuolar membranes. The Gomori acid phosphatase technique as combined with electron microscopy produced no evidence of autolysosomal segresomes in strands of intravacuolar reticulum of the cytoplasm.
INFLORESCENCE TYPES AND FRUITING PATTERNS IN HAMLIN AND VALENCIA ORANGES AND MARSH GRAPEFRUIT
Authors: Jahn Otto L.
Published: January 2018

The structural, flowering, and fruit‐setting patterns of inflorescences of mature Hamlin and Valencia orange and Marsh grapefruit trees were studied for three years. Several development patterns were found, some of which were relatively consistent for the different varieties or years of study. The sequence of anthesis on an inflorescence was: apical flower first, then basal flower, then the subapical flower. Terminals on which the earlier flowers appeared tended to have more inflorescences than those on which flowers appeared later. Inflorescences on which earlier flowers appeared also produced more flowers than those which began flowering later. Inflorescences that began flowering later were more likely to have leaves or have a greater number of leaves than earlier inflorescences. More than half of the inflorescences carried no leaves, and most of these had one flower. No evidence of a relationship between number of flowers and length of the inflorescence was found. Fruit set occurred primarily during the latter part of the flowering period. Many fruit were set on inflorescences without leaves, but on the basis of percent of flowers setting fruit, inflorescences with leaves were more productive. The greatest fruit set occurred in the subapical position on the inflorescence. With growth changes these fruit often appeared to be developing in the apical position. These patterns generally differed little from year to year. Variations may have been due to the differences in the number of flowers produced by the trees. Results were also similar between Hamlin and Valencia oranges. Patterns on Marsh grapefruit resembled those for the oranges but were frequently less consistent.
A NUMERICAL TAXONOMIC STUDY OF THE GENUS PLATANUS BASED ON MORPHOLOGICAL AND PHENOLIC CHARACTERS
Authors: Hsiao Ju‐Ying
Published: January 2018

Forty‐two morphological and eighty chemical (phenolic) characters were employed on a numerical taxonomic study of the genus Platanus. Ten taxa were used for morphological study, and nine were available for chemical study. UPGA was employed for cluster analysis; correlation coefficients served as a measurement of the similarity between each OTU‐pair. Comparison was made for phenograms and graph diagrams of nine taxa based on morphological characters with those based on chemical characters. It has been found that the two agree with each other in many respects. Correlation coefficient between similarity matrices based on morphological and chemical characters is 0.573. The result generally supports the belief that taxa closely related on morphological grounds are similar biochemically. A systematic consideration of the genus has been made, based on the information available.
INFLUENCE OF MANNITOL ON ABSORPTION AND RETENTION OF RUBIDIUM BY EXCISED CORN ROOTS
Authors: Smith Richard C. , John Beverly H. St. , Parrondo Rolando
Published: January 2018

Excised root segments of corn were subjected to osmotic stress by immersion in solutions of mannitol before, during, or after a period of Rb absorption. Both the time course of uptake (or loss) and selectivity of uptake were studied. Stress before or during the absorption period reduced Rb absorption to 20 % or less of that of controls, whereas it had no detectable influence on the constancy and selectivity of uptake. Stress imposed following a period of Rb accumulation caused root segments to lose only slightly more Rb than controls during the first 30 min, after which rates of change were insignificant in both. Segments stressed after the Rbabsorption period retained from 70–90 % as much Rb as did the controls, even after two hours. The comparatively great quantitative difference between effect of stress on uptake and its effect on loss is interpreted to mean that the mechanism of stress‐induced reduction of ion absorption cannot be adequately explained on the sole basis of increased efflux of ions.
EFFECT OF TEMPERATURE AND DAYLENGTH ON PEROXIDASE AND MALATE (NAD) DEHYDROGENASE ISOZYME COMPOSITION IN TOBACCO LEAF EXTRACTS
Authors: De Jong Donald W.
Published: January 2018

Tobacco plants were grown in controlled‐environment chambers with night/day temperatures of 10/15 C., 20/25 C., and 30/35 C., and with light durations of 6 hr, 12 hr, and 18 hr. Peroxidases and malate (NAD) dehydrogenases were extracted from green leaf tissue and analyzed for isozyme patterns by disc electrophoresis. A total of 18 anodic peroxidase bands were distinguishable—each alteration in a single environmental variable producing a different isozyme profile. Malate (NAD) dehydrogenase isozyme profiles resulting from each environmental condition exhibited at least four major components, but differences in daylength and temperature conditions changed the relative banding intensities and shifted migration rates of some bands. The physiological implications of these findings are discussed.
EFFECTS OF X IRRADIATION AND INDOLEACETIC ACID ON SPECIFIC PEROXIDASE ISOZYMES IN PITH TISSUE OF A NICOTIANA AMPHIPLOID
Authors: Chourey P. S. , Smith H. H. , Combatti N. C.
Published: January 2018

Two electrophoretically anodal peroxidase bands, designated A3 and A4, which normally develop in zymograms of incubated pith tissue of a Nicotiana amphiploid, were inhibited by the inclusion of 0.10 mg indoleacetic acid (IAA) in a liter of culture medium. The visibility of the bands was not inhibited, however, if the pith was irradiated or if unirradiated pith blocks were incubated in either irradiated IAA‐containing media or in media supplemented with irradiated IAA. Irradiation inactivates IAA in media, and according to this isozyme test, damages the capability in irradiated tissue of using exogenously supplied IAA. Radiationinduced damage to IAA metabolism caused radiation‐induced peroxidase stimulation, shown in the more rapid appearance of isozyme bands A3 and A4.
THE ACCUMULATION AND THE RELEASE OF DIVALENT CATIONS ACROSS MITOCHONDRIAL MEMBRANES
Authors: Johnson H. M. , Wilson R. H.
Published: January 2018

Accumulated divalent cations and phosphate (P1) in isolated bean mitochondria are released by conditions which inhibit respiration, including anaerobiosis and KCN, or by conditions which divert conserved energy from divalent cation uptake. These include ATP synthesis, KT transport in the presence of valinomycin, and the presence of the uncouplers, 2,4‐dinitrophenol and oleic acid. The results indicate that plant mitochondria are not permanent deposit sites for divalent cation and P1 salts but, rather, function as temporary sequestering sites for these ions. It is suggested that mitochondria may play a role in the control of the movement as well as a regulation of the concentrations of these ions within the cell.
POST‐POLLINATION PHENOMENA IN ORCHID FLOWERS. IV. EFFECTS OF ETHYLENE
Authors: Arditti Joseph , Hogan Nanette M. , Chadwick Arthur V.
Published: January 2018

Treatment of Cymbidium (Orchidaceae) flowers with 10/μl/liter ethylene for up to 78 hr induces anthocyanin formation in both gynostemia (columns) and labella (lips). After that, pigment levels decrease. During 24‐hr exposures, ethylene concentrations of 0.1, 1, and 10μl/ liter cause increased anthocyanin levels in both lips and columns. Ethylene also brings about color changes in the calli and wilting of the perianth, but it does not cause straightening of gynostemia and stigmatic closure. Emasculation effects are similar to those of ethylene, whereas pollination and NAA induce anthocyanin formation and closing of stigmas, as well as swelling and loss of curvature in gynostemia. The effects of ethylene are correlated with its action in other systems.
STUDIES OF SPHENOPHYLLUM SHOOTS: SPECIES DELIMITATION WITHIN THE TAXON SPHENOPHYLLUM
Authors: Good Charles W.
Published: January 2018

Structurally preserved ultimate vegetative shoots and attached foliage of Sphenophyllum multirame and two additional taxa from Upper and Middle Pennsylvanian coal balls are described. Shoot axes of all taxa are delimited by small cube‐shaped epidermal cells and contain three isolated strands of protoxylem tracheids separated by undifferentiated procambial cells. Metaxylem maturation is delayed for some distance below the apical meristem. Branches originate from a single protoxylem strand and are contiguous with the subjacent leaf trace for a short distance. Sphenophyllum multirame is considered a valid taxon. It is suggested that shoot and foliar anatomical characteristics may form valid criteria for species delimitation within the genus, and S. reedae is delimited by such characteristics. An additional form is tentatively suggested as a possible new species. Anatomical similarities between 5. reedae and Peltastrobus reedae suggest that these taxa represent vegetative and reproductive structures of the same plant.
DEVELOPMENT OF FOLIAR DIAPHRAGMS IN SPARGANIUM EURYCARPUM
Authors: Kaul Robert B.
Published: January 2018

Three types of diaphragms are produced in regular sequence by the basal intercalary meristem in the leaf of Sparganium eurycarpum Engelm. (Sparganiaceae). They bridge compartments formed by the collapse and disintegration of rib meristem derivatives. The adaptive nature of diaphragms, intercalary meristems, and linear photosynthetic organs is considered for emergent aquatic plants.
THE ECOLOGY OF CHONDRUS CRISPUS AT PLYMOUTH, MASSACHUSETTS. I. ONTOGENY, VEGETATIVE ANATOMY, REPRODUCTION, AND LIFE CYCLE
Authors: Prince Jeffrey S. , Kingsbury John M.
Published: January 2018

Carpospores and tetraspores germinate and the germlings develop similarly. A prostrate holdfast of regular or irregular outline is formed if the spore makes direct contact with the substrate. If not, rhizoids grow from the few‐celled germling unilaterally in no apparent relation to light or gravity, forming a prostrate holdfast if they encounter a solid substrate, and, in any case, eventually an erect shoot of different anatomy. Tetrasporophytes have been grown to reproductive maturity from single spore cultures in the laboratory. The ontogeny of the procarp and subsequent postfertilization events are described from field material. Only a single putative male plant was found when plants bearing procarps were numerous at Plymouth. Evidence from this study and from other reported observations places in doubt the expected role of fertilization in the diphasic, cytological alternation of Chondrus.
THE ECOLOGY OF CHONDRUS CRISPUS AT PLYMOUTH, MASSACHUSETTS. II. FIELD STUDIES
Authors: Prince Jeffrey S. , Kingsbury John M.
Published: January 2018

Growth and reproduction were examined periodically through a full year at four stations located in a dense population of Chondrus. Growth rates of germlings and of mature plants reach a maximum in late summer and a minimum in winter, paralleling temperature. At the time of maximum growth, nitrate is at its lowest seasonal concentration. Ammonia, however, is available and apparently utilized. Fronds are smaller but more numerous at −3 m MLW than at −6 m MLW and deeper and regrow from holdfasts with twice the original density after removal. Large fronds are torn off by storms at lesser depths. The average weight and density varies with season and possibly with depth. Chondrus at Plymouth is similar to populations investigated elsewhere in average density of plants per unit area, but the average weight per unit area was approximately twice that reported for other populations. Presence or absence of sori gives a false picture of reproductive periodicity because at some seasons most sori are empty or contain non‐viable spores. Carposporic reproduction reached a sharp maximum in October. Tetrasporic reproduction did likewise, with an additional lesser peak in May. At the time of greatest reproductive intensity, approximately half of all mature plants were shedding spores. Spores settle, germinate, and produce germlings successfully on initially sterile surfaces; no prior macroscopic or microscopic successional events are required. Seasonal composition of associated flora and epiphytes of Chondrus are discussed.
TAXONOMIC SIGNIFICANCE OF INTRASPECIFIC ISOZYME PATTERNS OF THE SLIME MOLD FULIGO SEPTICA PRODUCED BY DISC ELECTROPHORESIS
Authors: Berry J. A. , Franke R. G.
Published: January 2018

Plasmodial extracts of 45 isolates of Fuligo septica (L.) Wiggers selected from diverse geographical areas were subjected to acrylamide disc electrophoresis. Profiles for ten enzymes and general protein were determined. Profile variability among isolates occurred. Indices of similarity calculated for each isolate indicated that the variations of the yellow and white plasmodial isolates fell within different ranges. Determination of the total range of variation for the species must wait on the analysis of more white isolates. The extreme sensitivity of disc electrophoresis in detecting color forms suggests it can be useful as a tool in myxomycete taxonomy.
ULTRASTRUCTURAL CHANGES OF PLANTS EXPOSED TO LOW TEMPERATURES
Authors: Kimball Steven L. , Salisbury Frank B.
Published: January 2018

Effects of low temperatures on cell ultrastructures of three grass species were studied. Secale cereale L., Cynodon dactylon (L.) Pers., and Paspalum notatum Flugge seedlings were given treatments of −5, 0, 10, or 25 C for 3 days and then evaluated for cellular response. Electron micrographs showed chloroplasts to be the most sensitive organelle in all three species, with the temperate Secale plastids responding differently than plastids from the subtropical and tropical species. Rough endoplasmic reticulum increased, but dictyosome numbers decreased in all species as treatment temperatures were lowered to 0 C. Mitochondria expanded slightly at reduced temperatures, but with little difference detected between species. The study indicated that the various cellular components of these species responded differently to reduced temperatures, with the species differing mainly in degree of response.
SEASONAL VARIATION IN THE VOLATILE TERPENOIDS OF JUNIPERUS SCOPULORUM (CUPRESSACEAE)
Authors: Powell Rose Ann , Adams Robert P.
Published: January 2018

Fifteen trees in a natural population of Juniperus scopulorum Sarg. were sampled at 4‐week intervals throughout a year and the terpenoid constituents were extracted from the foliage. Several environmental variables were measured. Correlations with changes in volatile oil composition (computed as both relative percentages and as weights) were examined. Significant seasonal variations were discovered in both the relative percentage and weight data. These seasonal changes in the volatile oil composition were correlated with linear growth, temperature, yield of volatile oil, and dry weight of foliage. Seasonal variation in the terpenoids computed on a weight basis was found to be greater than the seasonal variation of the terpenoids computed as relative percents of the total oil. Evidence is presented which indicates that there is no stable period to sample on a weight basis, but sampling in the late fall and winter periods minimizes variation in the relative percentage data. The use of relative percentage data is thus encouraged for chemosystematic studies.
CHROMOPLAST ULTRASTRUCTURE AS AFFECTED BY GENES CONTROLLING GRANA RETENTION AND CAROTENOIDS IN FRUITS OF CAPSICUM ANNUUM
Authors: Laborde Jose A. , Spurr Arthur R.
Published: January 2018

Plastids in the fruits of isogenic lines of pepper (Capsicum annuum) were examined by electron microscopy with reference to four genotypes determining the carotenoid composition and the colors red, yellow, brown, and green of the ripe fruit. One gene pair (y+/y) influences carotenoid content and the other pair (cl+/cl) controls the chlorophyll. The retention of the grana and chlorophyll in the ripe fruits of the brown and green phenotypes is correlated with the cl cl genotype. The y+ gene increases the total carotenoids and promotes the formation of red pigments. Giant grana were found in the yellow and green phenotypes, but during ripening these disappeared in the yellow. Unusual dichotomous and concentric grana were observed in the green. Globule‐associated carotenoids forming fibrillar crystalloids were present in all color types, although to a lesser degree in the yellow fruit. Membrane‐associated carotenoids occurred only in the yellow and green phenotypes.
FLORAL STRUCTURE AND EVOLUTION IN LOPEZIEAE (ONAGRACEAE)
Authors: Eyde Richard H. , Morgan Judy T.
Published: January 2018

The Lopezieae present an interesting mixture of ancestral and derived characters: some members of the tribe retain the basic onagraceous chromosome number (n = 11), but the flowers are advanced in that they are mostly zygomorphic and always have a two‐merous androecium. Species differ in the position of the nectaries, also in the way in which floral parts are united above the inferior ovary. These differences, when analyzed with information from a new monograph of the Lopezieae, provide the basis for a phylogenetic tree. It is inferred that ancestral Lopezieae were bird‐pollinated woody perennials with regular flowers, two fertile stamens, and no floral tube distal to the ovary. Evolutionary events accompanying the emergence of modern taxa included abortion of the abaxial stamen (all surviving Lopezieae except Lopezia lopezioides), development of an epigynous floral tube (L. riesenbachia, L. semeiandra), decrease in floral symmetry without conversion to insect pollination (in two independent lines), and decrease in floral symmetry with conversion to insect pollination (in at least two independent lines). The prominent tubercles on upper petals of certain insect‐pollinated species apparently evolved from the less prominent swollen areas still present in some of the bird‐pollinated species. The tubercles and an associated snapping mechanism arose in response to increasing selection for fly pollination. Densely staining areas in some specimens may be osmophores; if so, scent plays a supplementary role in the orienting of insects to the upper petals. Interstaminal nectaries and the absence of a floral tube link the Lopezieae to Ludwigia; the relationship of these two taxa to Epilobium is presently unclear. Fossil records indicate that the Onagraceae had evolved by the beginning of the Tertiary Period and that the Ludwigia line is very old. The family's ancestral features are retained to a greater degree in Fuchsia, however, than in Ludwigia.
THE RELEASE MECHANISM AND LOCOMOTOR BEHAVIOR OF EQUISETUM SPERM
Authors: Bilderback Diane E. , Bilderback D. E. , Jahn T. L. , Fonseca J. R.
Published: January 2018

When antheridia of gametophytes of Equisetum hyemale L. are placed in water, only spermatid cells are released. These spermatid cells have from 6–12 fibrils radiating from 2–4 loci on the cell wall. One sperm is released from each spermatid cell. With high speed cinemicrography, it can be shown that sperm flagella beat three dimensionally with a continuous, traveling helical wave. A flagellar beat cycle is completed every 0.03 sec. In water the sperm swim rapidly at a rate of 300 μ per sec and traverse a helical path of long wavelength and shallow amplitude. Calcium is essential for normal locomotor behavior. When calcium is chelated by ethylenediaminetetraacetate (EDTA), the sperm spin in place. All other monovalent and divalent ionic solutions tested cause the sperm to swim abnormally. Monovalent ionic solutions prevent the drastic change in sperm mobility patterns resulting from chelation by EDTA.