bluuebunny/crossref_metadata_2025 huggingface dataset:
COMPARATIVE ANATOMY OF THE ASPIDIACEAE. I. STELAR PATTERN DEVELOPMENT IN YOUNG SPOROPHYTES OF TECTARIA
Authors: White Richard A.
Published: January 2018

Vascular tissue development in young sporophytes of seven species of Tectaria is described. Special emphasis is placed on stelar‐pattern ontogeny, the transition region between the primary root and the shoot, and changes in the nodal pattern associated with the sequential production of leaves. The changes in stelar pattern which occur prior to the production of the 8th leaf can be placed in three general categories. In the simplest category, development progresses from a protostele to a siphonostele with a unilacunar one‐trace nodal pattern. Species in a second category pass through the one trace per gap pattern to a siphonostele with a unilacunar two‐trace nodal pattern. The most complex category includes two species in which by the 3rd or 4th leaf a dictyostele with a unilacunar two‐trace nodal pattern is established. The significance of this pattern variation in young Tectaria sporophytes of equivalent stages in relation to taxonomic problems in the Aspidiaceae is discussed. In addition, the occurrence of a unilacunar one‐trace nodal pattern in these and other species of leptosporangiate ferns is related to the standard concept that a unilacunar two‐trace nodal pattern is basic in the ferns.
SEEDLING DEVELOPMENT OF OPUNTIA BRADTIANA (CACTACEAE)
Authors: Hamilton Margaret W.
Published: January 2018

Seedling development in Opuntia bradtiana, a north‐central Mexican endemic, is similar to that of other opuntias, except for the absence of glochids and the fact that germination is extremely slow and germination percentage low. Hypocotyl and root elongation and epicotyl development are rapid for two weeks after rupture of the seed coat. However at this point hypocotyl elongation nearly ceases, while stem and root development continue at a reduced rate. An eight‐month seedling is usually not more than 25 mm tall but has numerous areoles with spines and occasionally one subtending leaf. At this time tubercles have begun to coalesce into the vertical rows of ribs characteristic of the section Grusonia.
CHROMOSOME NUMBERS IN THE MALVALES. II. NEW OR OTHERWISE NOTEWORTHY COUNTS RELEVANT TO CLASSIFICATION IN THE MALVACEAE, TRIBE MALVEAE
Authors: Bates David M. , Blanchard Orland J.
Published: January 2018

Forty‐six chromosome counts from 29 species in 15 genera of Malvaceae, tribe Malveae are reported. Counts from 28 species and four genera, Bakeridesia Hochr., Hoheria A. Cunn., Plagianthus J. R. and G. Forster, and Robinsonella Rose and Baker, are new. These counts provide a basis for modifying a generic classification of the Malveae proposed by Bates in 1968. The identificaton of a heretofore unsuspected base chromosome number of x = 15, perhaps of ancient polyploid origin, has resulted in the realignment of Anoda Cav., Bakeridesia, Callirhoë Nutt., Napaea L., Periptera DC., and Sidalcea A. Gray. The data also support the thesis that the base chromosome number of the Malveae, or at least of the Abutilon alliance, is x = 8; that the genera of the New Zealand and Australian Plagianthus alliance were probably derived from abutiloid ancestors; that the generic boundaries of Pseudoabutilon R. E. Fries and Wissadula Medic. require redefinition; and that the Chilean Malacothamnus chilensis (Gay) Krapov. is generically distinct from the North American species of that genus. Callirhoë may be cytologically the most complex genus of Malveae. It includes both euploid and aneuploid series, probably supernumerary chromosomes, and perhaps structural rearrangements in the form of reciprocal trans‐locations between non‐homologous chromosomes.
STRUCTURAL AND HISTOLOGICAL STUDIES OF THE CAMBIUM AND SHOOT MERISTEMS OF SOYBEAN TREATED WITH 2,3,5‐TRIIODOBENZOIC ACID
Authors: Krause Bernard F.
Published: January 2018

Flowering soybeans were sprayed at the tips with 50 ppm TIBA. Microscopic and macroscopic observations were made of the nodes, internodes, and shoot meristems every week for 4 wks after TIBA treatment. TIBA‐treated plants produced open flowers at the upper nodes 1 week earlier than did control plants. Accompanying this early flower development, the following changes occurred in the upper internodes, as compared to controls: (a) increased activity of the procambium; (b) rapid development of thick‐walled protophloem cells; (c) production of small vessels. Three weeks after treatment middle internodes of treated plants showed less cambial activity than did corresponding internodes of controls. The changes in the middle internodes of treated plants suggest a close correlation with increased flowering. Two weeks after treatment some lateral shoot apices at nodes nearest the main shoot apex exhibited the following changes, in contrast with controls: (a) development of conical apices with stack‐of‐brick‐like peripheral cells; (b) shrinkage of protoplasmic contents in some rib meristem cells and young pith cells; (c) frequent thickening of primary walls in young pith cells. Three weeks after treatment cells of lateral shoot meristems with conical axillary buds showed a denser stain for protein than did cells of corresponding meristems of controls. Floral apices in these meristems also stained more densely for protein than did similar apices in control plants. Together with early flower production in the upper nodes of treated plants, less starch occurred 2–3 weeks after treatment than in corresponding nodes of controls. Two to three weeks after treatment lateral shoot apices of both treated and control plants had numerous, large starch grains in the rib meristem, young pith, leaf and bud primordia, and developing flowers but few starch grains appeared in the tunica, corpus, and procambium.
CHROMOSOME HOMOLOGY IN SOME INTERCONTINENTAL HYBRIDS IN HIBISCUS SECT. FURCARIA
Authors: Menzel Margaret Y. , Martin Diana W.
Published: January 2018

Ten kinds of interspecific hybrids were obtained involving the following species: H. surattensis L. (2x, genome constitution BB), H. sudanensis Hochr. (2x, GG), and H. rostellatus Guill. and Perr. (4x, GGHH) from Africa; H. furcatus Roxb. non Willd. (8x) from India and Ceylon; H. furcellatus Lam. and H. bifurcatus Cav. (both 4x, PPQQ) from South America; and H. heterophyllus Vent. (6x) from Australia. Chromosome pairing in pollen mother cells (PMC's) at metaphase I in the 4x hybrids H. bifurcatus‐rostellatus and H. furcellatus‐rostellatus indicated that the parents have one genome in common (Q = G or H). Hibiscus furcatus was shown earlier to have a B genome; hybrids of H. surattensis‐sudanensis F1 X furcatus were hexaploid, having received an unreduced gamete from their hybrid parent, and had approximately 36 II, 36 I in PMC's. The genome formula of H. furcatus may therefore be designated BBGGWWZZ. The hybrid H. rostellatus‐furcatus (BGGHWZ) confirmed that H. furcatus has a G genome in common with H. rostellatus; pairing of the other three genomes was inconsistent, as was that in H. rostellatus‐heterophyllus. Some samples of the latter approached 36 II, 36 I, expected if H. heterophyllus were GGHHJJ; other samples had less pairing. Hibiscus furcatus‐heterophyllus hybrids apparently arose from unreduced gametes of H. heterophyllus and originated as decaploids rather than heptaploids; chromosome number was unstable in PMC's. Nevertheless, multivalents, especially trivalents, were frequent enough to suggest that H. furcatus and H. heterophyllus share G genomes. On the other hand, an 8x H. bifurcatus‐furcatus hybrid, which apparently arose from an unreduced gamete of H. bifurcatus, had a low multivalent frequency. Hybrids were obtained of H. heterophyllus X sudanensis and H. surattensis‐sudanensis X heterophyllus, but the plants were weak and were not analyzed cytologically. We suggest that the New World, African, Indian, and Australian genomes which retain a considerable degree of homology (G or H or both) were distributed by land prior to separation of the southern continents by continental drift.
THE TRANSITION FROM FILAMENTOUS TO TWO‐DIMENSIONAL GROWTH IN FERN GAMETOPHYTES. III. INTERACTION OF CELL ELONGATION AND CELL DIVISION
Authors: Davis Bill D.
Published: January 2018

Periodic cell divisions were induced in gametophytes of Pteridium aquilinum by daily irradiation with white light. In white‐dark cycles, the rate of cell division was promoted by increased time in white light; cell elongation was not affected. The time of transition to two‐dimensional growth (days to 5% 2‐D) was closely associated with the mitotic rate. For white‐red cycles, the rate of elongation was controlled by the intensity of red light (wavelengths over 550 nm). This increased elongation delayed the initiation of 2‐D development. In both cases the rate of transition to 2‐D growth was correlated with the amount of elongation per division.
HUMMINGBIRD DISPERSAL OF DELPHINIUM CARDINALE POLLEN TREATED WITH RADIOACTIVE IODINE
Authors: Schlising Robert A. , Turpin Randolph A.
Published: January 2018

A new technique has been employed to trace pollen dispersal in populations of Delphinium cardinale (Ranunculaceae), a herbaceous perennial native to southern California. Radioactive iodine (I131) was applied directly to fresh pollen on stamens of living plants and subsequently traced and recorded on other plants in the field. While absolute amounts of I131 or pollen dispersed were not determined, monitor detection showed that radioactive pollen was dispersed to open flowers (more often to the brightest flowers higher on the plants), and not randomly to stems or unopened flower buds. All dispersal was attributed to hummingbirds—the only observed flower visitors and pollen vectors for these plants. One very dense Delphinium population had almost 140 lambda of I131 applied over 8 days to 76 flowers on six plants in the center of an area 22 m in diam. One fourth of this area monitored after 30 hr showed radioactive pollen on flowers of 8.9% of the 271 flowering stems; 8 days after the first application of I131 another fourth of the area showed radioactivity on flowers of 58.2% of the 323 stems in it. A second study area 22 m in diam had 18 lambda of I131 applied to 18 flowers on one plant in the center; 64.2% of all (137) flowering stems in the area had radioactive pollen detectable 24 hr later. It is clear that pollen from very few flowers and plants can quickly reach a large proportion of the individuals in such populations. The strongly protandrous nature of the flowers, the frequent flower visits of nectar‐gathering hummingbirds, and the regular adhering of pollen to birds' chins suggest that cross pollination (xenogamy) regularly occurs in these delphiniums. Further study of such pollen vectors' habits and flight patterns, while using pollen tagged with I131, should lead to quantitative expressions of pollen (and gene) dispersal within and among spatially separated plant populations such as these.
LEAF ONTOGENY AS A FACTOR IN SUSCEPTIBILITY TO OZONE: AMINO ACID AND CARBOHYDRATE CHANGES DURING EXPANSION
Authors: Ting Irwin P. , Mukerji S. K.
Published: January 2018

During development (expansion), the cotton leaf passes through a stage in which it is highly susceptible to ozone. This period of susceptibility occurs after the maximum expansion rate but before complete expansion occurs. The period of maximum susceptibility corresponds to a minimum concentration of soluble sugars and free pool amino acids. Specific amino acids such as aspartate, serine, threonine, glutamate, asparagine, alanine, glycine, valine, isoleucine, leucine, histidine, and tryptophan tended to reach a minimum concentration at about the same time leaves were susceptible to ozone. Ozone exposure during the susceptible period is manifested by visible leaf flecking of the upper surface and a dramatic (up to 2 fold) increase in total free pool amino acids. Most individual amino acids tended to increase except for phenylalanine, alanine, phosphoserine, phosphoethanolamine, and ethanolamine. Soluble protein is decreased but not to the same extent that the free pool amino acids increase. Because there is ample evidence that ozone enters the leaf during nonsusceptible periods as well as susceptible periods, it is postulated that ozone damage results because of the depletion of soluble reserves (carbohydrates and amino acids). Perhaps repair of damage cannot occur.
DEVELOPMENT AND GAMETOPHORE INITIATION IN THE MOSS PYLAISIELLA SELWYNII AS INFLUENCED BY AGROBACTERIUM TUMEFACIENS
Authors: Spiess Luretta D. , Lippincott Barbara B. , Lippincott James A.
Published: January 2018

Spores of the heterotrichous moss Pylaisiella selwynii Kindb. were sown in a defined inorganic liquid culture medium and incubated at 27 C with a 16‐hr photoperiod. They germinated at 7–10 days, and formed a few caulonemal buds at 27–30 days which developed into gametophores by 40 days. Bud formation and gametophore development followed a pattern common to many mosses. Addition of a virulent strain of Agrobacterium tumefaciens (B6) to the moss cultures increased bud formation and hastened the time of their appearance by 5–6 days. With 109 or more bacteria per ml of moss culture medium the percentage of plants with gametophores at day 35 after the spores were sown was 96 % or greater, as opposed to 0–24 % in the controls. The mean number of gametophores per responding plant was also increased from one per plant in controls to 4–6 per plant in inoculated cultures. Addition of the bacterium at day 17–18 of culture was as effective as early additions of the bacterium, suggesting that the moss must become ready to bud before the bacterium can influence its development. The promotion of gametophore formation was directly related to the number of bacteria added and depended upon the presence of viable bacteria. The supernatant from bacterial cultures did not promote gametophore formation. The changes induced by A. tumefaciens were similar to those reported for cytokinins.
CHROMATOGRAPHIC COMPARISON OF TRAGOPOGON SPECIES AND HYBRIDS
Authors: Belzer Norbert F. , Ownbey Marion
Published: January 2018

Approximately 1,700 plants representing five species of Tragopogon (Compositae) and their F1 and F2 hybrids were analyzed by two‐dimensional descending paper chromatography. Each species, or population within a species, was chromatographically distinct. Often, however, the differences were more quantitative than qualitative. The chromatographic data generally supported the species relationships which had been determined from previous morphologic, hybridization, and fertility studies. Inheritance of the flavonoid compounds was usually additive in the F1's. Segregation and recombination of the genes controlling the synthesis of these compounds sometimes approximated 3:1 or 9:7 ratios in the F2's. Occasionally parental compounds were missing from some of the hybrids. “Hybrid” compounds which had not been found in either parent were absent from the F1 but did occur in several F2 populations. Two linkage groups were present. The first contains genes controlling the synthesis of three compounds and the second, four compounds.
DIAPHRAGMS AND AERENCHYMA IN SCIRPUS VALIDUS
Authors: Kaul Robert B.
Published: January 2018

After the short‐lived apical meristem ceases activity, a basal intercalary meristem produces all new tissues in the aerial internode of Scirpus validus Vahl. These include extensions of the original vascular system and of the original partitioning walls as well as new vascular bundles and new walls which are produced in a predictable pattern. Diaphragms begin to differentiate well within the intercalary meristem. At first their cells are indistinguishable from those that will become the aerenchyma, but they undergo segmentation and form packets of daughter cells. Such continued mitotic activity allows the diaphragms to expand with the increasing girth of the stem above the intercalary meristem. Aerenchyma cells between the diaphragms become stellate by being stretched as the cells of the vertical partitions divide and enlarge in and above the intercalary meristem.
THE CULTURE OF APICAL BUDS OF XANTHIUM AND THEIR USE AS A BIOASSAY FOR FLOWERING ACTIVITY OF ECDYSTERONE
Authors: Jacobs William P. , Suthers Hannah B.
Published: January 2018

Conditions were developed for the sterile culture of shoot tips of Xanthium pensylvanicum Wallr. for use as a bioassay for flower‐controlling chemicals. By using a modified Murashige‐Skoog medium (minus the auxin but including kinetin) and light intensity much higher than usual for plant tissue cultures, fast growth and development of the shoot tips was achieved. Under short‐day conditions (8 hr day: 16 hr night), the cultures from vegetative shoots flowered and fruited; under noninductive conditions (using a 2 hr light‐break in the middle of the dark period), the shoot tips continued vegetative development. Both intact plants and cultured tips could be photoinduced in the first days after germination. Ecdysterone, a potent insect moulting hormone, was tested in the bioassay system. It was without either qualitative or quantitative effect on flowering or vegetative development on either cultured shoot tips or intact plants irrespective of whether they were under inductive or noninductive photoperiodic conditions.
THE ETIOPLAST–CHLOROPLAST TRANSFORMATION IN TOBACCO: CORRELATION OF ULTRASTRUCTURE, REPLICATION, AND CHLOROPHYLL SYNTHESIS
Authors: Boasson Rosalinda , Laetsch W. M. , Price Ian
Published: January 2018

Plastid ultrastructure was correlated with plastid replication and growth during the greening of etiolated tobacco tissue. The plastids grow rapidly, and this growth is correlated with a period of rapid chlorophyll synthesis. Chlorophyll synthesis is correlated with the formation of grana. The plastids divide by constriction and continue to do so after most of the grana have been formed. They contain single membrane‐bound bodies, which are observed less frequently in the last stages of chloroplast maturation. No internal morphological features of the plastids appear to be related to causal aspects of replication.
DISTRIBUTION OF 3H‐THYMIDINE IN ARABIDOPSIS VEGETATIVE MERISTEMS AFTER 5‐IODODEOXYURIDINE TREATMENT
Authors: Brown John A. M.
Published: January 2018

Arabidopsis thaliana vegetative meristems, growing under short photoperiods, respond to the application of IUdR by precocious floral morphogenesis. 3H‐thymidine was used to label cells active in DNA synthesis and study the effect of analogue application on the amount and distribution of DNA synthesis throughout the meristem during 78 hr subsequent to IUdR treatment. Photomicrographs, autoradiographs, and composite plots of label distribution in transparent superimposed sequential sections revealed a non‐uniform distribution of labelling in control vegetative meristems, which typically contained a central and axial core incorporating little 3H‐thymidine and a peripheral flanking tunica region which contained densely labelled cells. The ratio of labelled cells in the peripheral region to labelled cells in the central region was about 10:1 in the controls. In meristems pretreated with IUdR there was a brief suppression of 3H‐thymidine incorporation during 6–12 hr after treatment, followed by two waves of enhanced incorporation in the peripheral region, and a progressive increase in the frequency of labelled cells in the central core of the meristem. After 78 hr the frequency of labelled cells in the central core of IUdR‐treated meristems was 8‐fold higher than in untreated meristems, and the frequency in the peripheral regions was about the same in both IUdR and control series. The enhancement in amount and uniformity of DNA synthesis after temporary inhibition by IUdR parallels the normal enhancement which is observed when vegetative meristems are transferred to long photoperiods causing floral induction.
OZONE DAMAGE TO PONDEROSA PINE: A HISTOLOGICAL AND HISTOCHEMICAL APPRAISAL
Authors: Evans Lance S. , Miller Paul R.
Published: January 2018

Histological and histochemical changes occurred in current‐year needles of sensitive clonal selections of Pinus ponderosa Laws under natural summer growing conditions in the San Bernardino National Forest near Los Angeles, California due to fumigations with 0.45 ppm ozone for 12 hr/day. Within five days after the start of fumigation, chloroplasts and carbohydrate stain accumulated in the peripheral portions of mesophyll cells. Concurrently, the homogenous distribution of proteins and nucleic acids was disrupted. Succinate dehydrogenase was localized mostly in guard cells, resin duct epithelial cells, albuminous cells, and differentiating vascular tissues within unfumigated and fumigated leaves. Acid phosphatase activity increased within mesophyll cells during ozone exposure, but there was no association of acid phosphatase or ozone injury with stomata. Wall destruction occurred in mesophyll cells after appreciable intracellular damage. These histological and histochemical changes occurred within 5–7 days, but visual symptoms were not evident until 2–3 weeks after fumigation. It is thus possible to assay ozone damage very soon after exposure if no other external agents cause similar results.
ZONATION IN THE APICAL CELL OF ZONARIA
Authors: Neushul M. , Dahl A. L.
Published: January 2018

Light and electron microscopic techniques were used to study the row of apical cells that form the meristem of the dictyotalean brown alga, Zonaria farlowii. A distinctly polar pattern occurs in the cells. Four ultrastructurally different cytoplasmic zones have been seen: an apical zone, a nuclear zone, a compound vacuolar zone, and a vegetative zone. The apical cell of Zonaria is a differentiating cytoplasmic unit where striking intracellular gradients occur.
ACTION OF FUSICOCCIN ON THE POTASSIUM BALANCE OF GUARD CELLS OF PHASEOLUS VULGARIS
Authors: Turner Neil C.
Published: January 2018

Fusicoccin induces stomatal opening in both the light and dark. The stomatal aperture and K content of guard cells was measured to determine whether the action of fusicoccin in inducing stomatal opening is directly related to the uptake of K by the guard cells. Both detached and attached epidermis was treated with fusicoccin and the K content was determined by staining with cobalt sodium nitrite or by electron probe microanalysis. The K content of guard cells in detached epidermal strips floated on 10 μm fusicoccin in 10 mm KCl and aqueous CH3OH (0.02%, v/v) increased in the light and dark as the stomata opened. After exposure to fusicoccin for 6 hr in the light, however, the stomata were closed and no K could be detected in the guard cells. The K content of guard cells of attached epidermis painted with fusicoccin also increased as the stomata opened, but the concentration of K in the subsidiary cells was not significantly altered by fusicoccin‐stimulated opening. Moreover, painting with fusicoccin did not significantly change the Ca and P content of the guard or subsidiary cells. Stomata of epidermal strips, opened to their maximum width by fusicoccin, showed only a small and temporary closure when transferred to a solution of 10 μm abscisic acid. The use of metabolic inhibitors suggested that energy for the uptake of the K may be provided by both photophosphorylation and oxidative phosphorylation.
STUDIES OF A MARINE GRASS, THALASSIA TESTUDINUM. I. ULTRASTRUCTURE OF THE OSMOREGULATORY LEAF CELLS
Authors: Jagels Richard
Published: January 2018

Thalassia testudinum (Turtle Grass), a marine monocot which grows completely submerged, differs from intertidal and other halophytic angiosperms in that it has no specialized saltsecretory glands. Osmoregulation appears to be accomplished by the epidermal leaf cells which have highly invaginated plasmalemmas with numerous mitochondria situated in the interdigitations. The ultrastructure and proposed mode of secretion are similar to that of the salt‐marsh monocot Spartina, but differ from that found in dicots. Evidence is presented to show why monocots are the only angiosperms which have adapted to a completely marine environment.
OZONE‐INDUCED MEMBRANE PERMEABILITY CHANGES
Authors: Evans Lance S. , Ting Irwin P.
Published: January 2018

The effect of 0.5 ppm ozone for 0.5‐1 hr on plant cell membrane permeability was ascertained. Permeabilities to both water and solutes were estimated by measuring leaf disc weight changes and following tritiated water and 86Rb fluxes. Measurements were made immediately after ozone exposure and 24 hr after exposure. The reflection coefficient, σ, an index of solute permeability, decreased in ozone‐treated primary leaves of pinto bean (Phaseolus vulgaris). The latter indicates an increase in membrane solute permeability or internal solute leakage. Water and THO flux estimates both indicated a decrease in membrane permeability to water; both the hydraulic conductivity (Lp) and the water diffusional coefficient (LD) apparently decreased, an anomaly which is discussed. These data indicate that ozone has a direct effect on membrane function by altering permeability characteristics. We assume from these data that cell membranes are primary target sites for ozone injury.
STOMATAL PENETRATION: EFFECT OF SURFACTANTS AND ROLE IN FOLIAR ABSORPTION
Authors: Greene Duane W. , Bukovac Martin J.
Published: January 2018

Stomatal penetration of aqueous solutions into pear (Pyrus communis L. cv. Bartlett) leaves was induced with surfactants. The effectiveness of surfactants in promoting stomatal penetration was related to their effectiveness in decreasing surface tension. Vatsol OT (dioctyl ester of sodium sulfosuccinic acid) was most effective, X‐77 (compounded product of alkyl aryl polyethoxy ethanol, free fatty acids and isopropanol) intermediate, and Tween 20 (polyoxyethylene sorbitan monolaurate) least effective. The percentage of stomata penetrated was limited, ranging from 0.5–4.5 %. There was no evidence of stomatal penetration of aqueous solutions with surface tensions of approximately 70 dyne cm−1. The importance of stomatal penetration in foliar absorption under conditions of plant culture is discussed.
STUDIES OF PACIFIC ISLAND PLANTS. XXVII. THE GENUS GARDENIA (RUBIACEAE) IN THE FIJIAN REGION
Authors: Smith Albert C.
Published: January 2018

The genus Gardenia (Rubiaceae), noted for its beautiful and fragrant flowers, is widespread throughout the Old World tropics. In the Fijian Region it is represented by eleven indigenous species, of which eight are endemic to Fiji; an additional oriental species is occasionally found in cultivation. The taxonomic relationships and nomenclature of these species are discussed, and one new Fijian species, G. anapetes, is described.
HYBRIDS AND INDUCED AMPHIPLOIDS OF ELYMUS CANADENSIS X AGROPYRON LIBANOTICUM
Authors: Dewey Douglas R.
Published: January 2018

North American Elymus canadensis L., 2n = 28, and Asian Agropyron libanoticum Hack., 2n = 14, crossed with ease and yielded vigorous but sterile F1 hybrids, 2n = 21. Chromosome pairing in the hybrids averaged 9.47I, 5.38II, and 0.26III in 150 metaphase‐I cells. One genome of E. canadensis is more or less homologous with the A. libanoticum genome. Treatment of the F1 hybrids with colchicine produced 42‐chromosome amphiploids, C0, which were advanced through two seed generations, C1 and C2. More than half of the metaphase‐I cells in the C0 amphiploids contained 21II; and average associations were 1.09I, 20.16II, 0.07III, and 0.09IV in 116 cells. Meiosis became increasingly irregular beyond metaphase‐I; nevertheless, the C0 amphiploids produced 68% stainable pollen and averaged 0.75 seed per spikelet. Multivalent frequencies increased in advanced generations, and the C2 amphiploids averaged 1.11I, 19.00II, 0.23III, and 0.55IV in 100 metaphase‐I cells. Meiosis was essentially regular in the C1 and C2 amphiploids beyond metaphase I, and the C2 amphiploids averaged 73% stainable pollen and 2.28 seeds per spikelet. The amphiploids have an excellent chance of developing into a meiotically stable, fertile, new species. Forage characteristics of the amphiploids indicate that they have considerable economic potential as a forage grass.
DIFFERENTIATION, ORGANOGENESIS, AND THE TECTONICS OF CELL WALL ORIENTATION. III. THEORETICAL CONSIDERATIONS OF CELL WALL MECHANICS
Authors: Lintilhac Philip M.
Published: January 2018

This paper is concerned with the relationship between cell wall orientation in dividing tissues and stress. An examination of the possible orientations of a cell‐plate in a cell under axial stress reveals that only one orientation passing through the center of the cell can be completely free from shear stress, thus providing a favored plane for the positioning of an hypothetical, shear‐sensitive, cell‐plate precursor. From this principle of shear‐free partitioning, and the three basic rules of stress behavior along free boundaries, it is possible to predict certain features of cell wall orientation along free edges and epidermal surfaces and in some simple apices. The possible significance of the widespread phenomenon of axillary induction of bud formation is discussed in terms of the generation of stresses at the base of the axillant leaf, and the general efficacy of mechanical stress as a spontaneously arising morphogenetic trigger is considered.
AQUATIC FUNGI OF ICELAND: ACHLYA AMERICANA
Authors: Johnson T. W. , Seymour R. L.
Published: January 2018

Twenty‐one isolates of Achlya with smooth‐walled oogonia, small, eccentric oospores, and a preponderance of monoclinous antheridial branches are characterized quantitatively and qualitatively. The isolates are separated into nine series, and the parameters through which they relate to and digress from one another are discussed. At most, three quantitative characteristics separate the various groups. The distinctive features of isolates in two series are unstable in culture. A concept of broad species limits is applied to A. americana.
SPORE WALL FORMATION AND CHLOROPLAST DEVELOPMENT DURING SPOROGENESIS IN THE MOSS FISSIDENS LIMBATUS
Authors: Mueller Dale M. J.
Published: January 2018

The sequence of wall formation in spores of Fissidens limbatus Sullivant is as follows: The exine is formed around the protoplasts after the sporocyte has undergone meiosis. The fully enlarged spores then become coated by the perine; this is followed by intine formation. The source of the intine and exine appears to be from within the spore, but the perine is of an apparent exogenous origin. Ornamentation of the spore is due solely to deposition of the perine. Each spore originally has a single plastid. Plastids increase in number by fission, resulting in mature spores with numerous plastids with well differentiated lamellae.
SHOOT ORGANIZATION IN THE FILICALES: THE PROMERISTEM
Authors: McAlpin Bruce W. , White Richard A.
Published: January 2018

The classical pteridophyte apical cell theory of meristem organization is not flexible or realistic enough to encompass the variation encountered in a comprehensive anatomical survey of fern meristems. The meristems of 28 taxa of ferns (both eu‐ and leptosporangiate) were studied. This analysis has led to the formulation of the concept of a promeristem composed of two zones: the surface and subsurface initials. This concept is flexible and sufficient to describe the variation encountered in the ferns as a group. No differences in promeristem organization were observed in plants with various rhizome morphology (e.g., upright and radial; prostrate and dorsiventral). Marking experiments, performed on living surface cells of fern promeristems, correlate with anatomical observations of division planes in the promeristem and indicate that the central, surface initials are not quiescent. Feulgen determinations indicate that Nephrolepis stolons have no endomitotically polyploid cells in the promeristem. Additional work is needed before a generalization can be made concerning ploidy levels in a more typical fern apex. Ferns, in general, have a zoned promeristem which is parallel to the zonation described for higher vascular plants.
VARIATION IN THE NUTRIENT CONTENT OF LEAVES OF QUERCUS ALBA, QUERCUS COCCINEA, AND PINUS RIGIDA IN THE BROOKHAVEN FOREST FROM BUD‐BREAK TO ABSCISSION
Authors: Woodwell G. M.
Published: January 2018

Leaves of Quercus coccinea, Q. alba, and Pinus rigida were collected at six dates during the growing season and analyzed for N, P, K, Ca, Mg, Fe, S, and Na. Leaf weights per unit of leaf area (or length) were determined for the same period. Quercus coccinea and Q. alba leaves increased in weight per unit area by about 30 % and 50 %, respectively. First‐year pine leaves increased in weight per unit length by about 65 %. During the second year the weight of pine leaves changed little. Two broad patterns in the nutrient content of leaves were apparent when nutrient content was expressed on the basis of leaf area rather than leaf weight. N, P, and K concentrations increased to a peak in mid‐ or late summer and declined abruptly just prior to abscission. Concentrations of other elements tended to rise slowly throughout the life of the leaves in all three species. The differences among nutrients and among species support the hypothesis that differential partitioning of the nutrient pool occurs as a result of evolutionary adaptation. The changes in weight of leaves per unit area and in nutrient content during the growing season are important for studies of net primary production and in appraisals of the cycling of nutrients. Least distortion of nutrient relationships occurs when area or length of leaf is used as the basis for expression of nutrient content.
MORPHOLOGY, FINE STRUCTURE, AND ONTOGENY OF THE STINGING EMERGENCE OF URTICA DIOICA
Authors: Thurston E. Laurence
Published: January 2018

Stinging emergences in Urtica dioica L. characteristically possess an elongate stinging cell and a multicellular pedestal. The emergence is derived from the epidermal and subepidermal cell layers. The apical wall of the stinging cell is composed of silica bodies which decrease basipetally in concentration. The basal portion of the cell wall of the stinging cell is devoid of silica bodies and lacks primary pit fields or pits between it and the pedestal cells. X‐ray microanalysis of electron dense particles located in the stinging cell ER‐golgi complex indicate that these particles contain silicon. There is no ultrastructural evidence for the presence of a toxin synthesizing system or a toxin itself.
ULTRASTRUCTURAL ALTERATIONS IN OAK LEAVES PARASITIZED BY TAPHRINA CAERULESCENS
Authors: Camp R. R. , Whittingham W. F.
Published: January 2018

Leaves of Quercus velutina Lam. parasitized by Taphrina caerulescens (Desm.) Tulanse were examined with the electron microscope to ascertain cellular aberrations that were induced by the fungus. Major changes were most apparent in the lower epidermis, where cellular divisions and enlargement were common, the cell walls becoming irregularly thickened. Many of the ultrastructural features of the diseased cells resembled those of meristematic cells; the absence of a large central vacuole, a disproportionately large nucleus, and an abundance of cytoplasmic organelles. Chloroplasts with large amounts of starch were also routinely observed.
THE POLLINATION ECOLOGY OF DELPHINIUM TRICORNE (RANUNCUL ACEAE)
Authors: Macior Lazarus Walter
Published: January 2018

The pollination ecology of Delphinium tricorne, a spring‐ephemeral herb of eastern deciduous forests, was studied at eight sites in the Ohio River basin from West Virginia to southern Illinois. The plant was found to be obligately dependent for its pollination on queen bumblebees (Bombus Latr. spp.) and hummingbirds, to which the flowers are closely adapted in form, color, function, and blooming phenology. Other bees, including Anthophora ursina, Osmia bucephala, Ptilothrix bombiformis, and Xylocopa virginica; Lepidoptera, including Amphion nessus, Danaus plexippus, Epargyreus clams, Erynnis juvenalis, Hemaris thysbe, Papilio glaucus, P. philenor, P. troilus, Poanes zabulon, Vanessa atalanta, and V. cardui; and the beefly Bombylius major foraged for nectar and/or pollen on the flowers without pollinating them. Techniques employed in the study included insect exclosures to test fertility of plants in the absence of pollinators, analysis of floral colors by reflectance spectrophotometry and ultraviolet photography, analysis of pollinator behavior by cinematography and close‐range stereophotography, collection and identification of visitors to flowers, and identification of pollen types carried by foragers on the flowers.
EXPERIMENTAL HYBRIDIZATION OF XANTHIUM STRUMARIUM (COMPOSITAE) FROM ASIA AND AMERICA. I. RESPONSES OF F1 HYBRIDS TO PHOTOPERIOD AND TEMPERATURE
Authors: McMillan Calvin
Published: January 2018

Responses to photoperiod and temperature were compared for hybrids between Asiatic plants in the indigenous strumarium morphological complex and plants in five American complexes: oviforme, italicum, chinense, cavanillesii, and pennsylvancium. The F1 hybrids between Hong Kong plants and various American plants showed intermediacy in photoperiodic response; however, the hybrid night requirement was more similar to that of the American parent. The Hong Kong plants are difficult to evaluate photoperiodically but showed a night length requirement of 9.25–9.50 hr. Day‐neutral plants from India in the strumarium complex produced day‐neutral F1 hybrids in crosses with most American plants having night requirements less than 10 hr. The F1 hybrids involving the day‐neutral Indian plants and either Indian or Australian chinense plants showed a night requirement of 8.25–8.75 hr. The chinense parental plants had apparent critical nights of 10.25–10.50 hr. Crosses between the day‐neutral Indian plants and Mexican plants with apparent critical nights of 10.75–11 hr produced F1 hybrids requiring nights of 8.75–9.00 hr. The various hybrids tended to show the broader temperature tolerances of the American parents. The ripeness‐to‐flower (maturity) responses of seedlings tended to show the genetic controls of the parent with the faster developmental rate. The hybridization evidence suggests that photoperiodic responses are quantitatively controlled and inherited independently of morphology and ripeness‐to‐flower responses. The populations of India are highly diverse and probably reflect recombinations of photoperiodic and temperature responses between indigenous day‐neutral plants and photoperiodic chinense plants introduced from North America.
THE INFLUENCE OF SPECIMEN TOPOGRAPHY ON X‐RAY MICROANALYSIS ELEMENT MAPPING
Authors: Hess F. D. , Falk R. H. , Bayer D. E.
Published: January 2018

The effect of specimen topography on x‐ray microanalysis element mapping was studied with an electron microprobe and a scanning electron microscope equipped for x‐ray detection. Using the lemma and palea of rice inflorescences as models, we determined that specimen topography can physically limit the detection of x‐rays and thus lead to erroneous element mapping data. Any geometrical point on a specimen interfering with a straight line from the point of excitation to the detector will cause an absorptive shadow area on the element map. Electrons impinging on a sample surface cause emissions to occur in all directions. Emissions with sufficient energy (x‐rays and backscattered electrons) can strike a topographical point different from the location of the focused electron beam, causing detectable x‐ray excitation. This phenomenon will also result in erroneous element map data. Methods of recognition of specimen topographical effects on x‐ray microanalysis are discussed.
EARLY HISTOGENESIS OF THE ADULT LEAVES OF DARLINGTONIA CALIFORNICA (SARRACENIACEAE) AND ITS BEARING ON THE NATURE OF EPIASCIDIATE FOLIAR APPENDAGES
Authors: Franck Daniel H.
Published: January 2018

In order to assess the validity of various interpretations of tubular leaves of angiosperms, a histogenetic study of the ontogeny of adult leaves of Darlingtonia californica was undertaken. The adult leaf of Darlingtonia is characterized by a sheathing leaf base, an elongate ascidium, an overarching hood, and two “fishtail” appendages which arise near the leaf apex. A keellike growth, with two rows of alternate vascular bundles, traverses the tube from base to mouth. Ontogenetic studies show that the primordium arises by a monopodial rather than a sympodial mode of growth as previously reported. After the formation of a small, erect primordium, a restricted adaxial meristem is initiated that expands both adaxially and upwards. This “querzone” serves, in effect, to congenitally combine the two primordial margins during its extension. Growth and maturation of the subjacent portions cause tubular elongation in the leaf. Primordial apical divisions are later replaced by more general intercalary growth with acropetal and centrifugal maturation. The hood and fishtails are established early in ontogeny by adaxial growth of the primordial apex and subsequent activation of juxtaposed localized meristems. Comparative morphology has established that the epiascidiate leaf is a foliar appendage that undergoes certain specific morphogenetic modifications. It has a structural relationship to ensiform appendages of Acacia and Acorus as well as to peltate foliar organs. The early ontogeny of Darlingtonia leaves is considered to be homologous with other epiascidiate foliar organs, including some supposedly primitive carpels.
FINE STRUCTURE OF CHLOROPLASTS IN “GREEN ISLANDS” AND IN SURROUNDING CHLOROTIC AREAS OF BARLEY LEAVES INFECTED BY POWDERY MILDEW
Authors: Camp R. R. , Whittingham W. F.
Published: January 2018

The fine structure of mesophyll chloroplasts in green islands and in adjacent chlorotic areas of barley leaves infected with Erysiphe graminis (DC.) was compared with healthy non‐inoculated tissue. Chloroplasts in green islands were persistent. Green‐island chloroplast grana were enlarged and fewer in number than in healthy tissue. In contrast, cells in chlorotic areas had fewer chloroplasts and their lamellae showed progressive degeneration and fragmentation. The lamellae often resembled aberrant prolamellar bodies. As lamellar degeneration progressed there was a marked increase in the amount of osmophilic material within the chloroplasts.
THE FOLIAR AND FLORAL NECTARIES OF TURNERA ULMIFOLIA L.
Authors: Elias Thomas S. , Rozich W. R. , Newcombe Lydia
Published: January 2018

The floral and foliar nectaries of Turnera ulmifolia are specialized and are representative of others found in the Turneraceae. The foliar and floral nectary systems must be treated independently. Foliar nectaries are organized into a definite structure (composed of a base, rim, secretory tissue, modified epidermis) and are supplied with vascular tissue composed of both xylem and phloem. Nectar from foliar nectaries contained equal concentrations of glucose, fructose, and sucrose. Floral nectaries are an integral part of the basal portion of each filament. The nectariferous tissue is not supplied with vascular tissue and secretion lasts only a few hours. Nectar from these staminal nectaries yielded a sucrose‐dominant nectar containing also fructose, glucose, an unknown, and a trace amount of melezitose. Observations of flowering confirmed the reported short duration of the individual flowers.
GROWTH REGULATOR EFFECTS ON BUD INITIATION IN CALLUS CULTURES OF MEDICAGO SATIVA
Authors: Saunders J. W. , Bingham E. T.
Published: January 2018

Influence of growth regulators on bud initiation in callus of alfalfa (Medicago sativa L.) was studied by varying levels and combinations in the first medium of a two‐medium sequence used to obtain whole plants. Callus of tetraploid clone S‐4 (cv. ‘Saranac‘) was initiated from immature ovaries on a modified Blaydes' basal medium containing all combinations of six concentrations (0–36 μM) of kinetin (K), six concentrations (0–44 μM) of naphthaleneacetic acid (NAA), and seven concentrations (0–36 μM) of 2,4‐dichlorophenoxyacetic acid (2,4‐D). After 28 days the callus was challenged to form buds by transfer to the modified Blaydes' medium containing 2.0 g/liter yeast extract and 0.57 mM inositol. No buds were produced in the absence of 2,4‐D in the first medium, and the frequency of bud formation on the second medium was directly proportional to the 2,4‐D concentration in the range 2.3–54 μM in the preceding medium. Buds were produced in the absence of kinetin in the first medium, but its presence in the range 2.3–36 μM markedly increased bud formation. NAA was not required for bud formation, and the budding frequency increased only slightly with increasing NAA concentration in the first medium. Budding of callus of two other alfalfa clones was also influenced by the 2,4‐D concentration in the initial medium. There were several indications that many of the buds were initiated on the first medium and completed development on the second medium. These included the differential effect on budding of combinations of 2,4‐D, NAA and kinetin in the callus initiation medium, the specific media sequence required, and the presence of embryoids on the callus which after transfer to the yeast extract‐inositol medium produced buds.
GROWTH AND METABOLISM OF THE EMBRYO AND ATTACHED SEEDLING OF THE VIVIPAROUS MANGROVE, RHIZOPHORA MANGLE
Authors: Sussex I.
Published: January 2018

Fruits of Rhizophora mangle were collected at various stages of development, separated into fruit wall, testa, and embryo or seedling. Wet weight, dry weight, and percent water content was determined for each. All parts of the fruit showed a similar growth pattern with a period of rapid exponential growth during the first 100 days, followed by a period of slower growth after the radicle‐hypocotyl axis emerged through the fruit wall. In the final 45 days of seedling attachment the fruit wall and testa did not grow, and seedling growth rate was further reduced. Water content of the fruit wall was constant at 65 % throughout development; that of the testa decreased uniformly from 60 to 54%; embryo water content was uniformly 80%. In the germinated seedling, water content declined progressively to 58 % by the time detachment occurred. Growth of isolated seedlings in sterile culture was not responsive to inhibition by abscisic acid or to stimulation by benzyl adenine, and these hormones had no effect on incorporation of 3H‐amino acids into protein or of 3H‐uridine into RNA. These results are interpreted in relation to a theory which proposes that development of water stress in the seed is the signal for the inception of dormancy.