bluuebunny/crossref_metadata_2025 huggingface dataset:
DEVELOPMENTAL STUDIES IN PTYCHOSPERMA (PALMAE). II. THE STAMINATE AND PISTILLATE FLOWERS
Authors: Uhl Natalie W.
Published: January 2018

The staminate flower of Ptychosperma mooreanum and P. gracile has three imbricate sepals, three valvate petals, an androecium of 9–13 or 27–32 stamens, and a lageniform pistillode. Pistillate flowers have three imbricate sepals, but the three petals are also imbricate, and the three (‐seven) staminodes are irregular and sometimes basally fused. The ovoid pseudomonomerous pistil has a single locule with a pendulous ovule and three small distal stigmatic lobes. All floral organs are initiated by periclinal divisions in the second tunica layer of the floral apex, with divisions in the outer layer of the cortex also apparent in the initiation of stamens and staminodes. Primordia of floral organs differ in shape but can be related to those of other palm flowers. Sepals are initiated and develop successively, and during floral organogenesis are horizontally oriented covering other organs. Petals are also initiated successively, but rapidly attain equal size. Petals of staminate and pistillate flowers are initially similar, but subsequent prolonged activity of marginal meristems results in widely imbricate petals in pistillate flowers. The polyandric androecia are clearly trimerous. As stamen initiation commences, the apex is divided into sectors or primary primordia consisting of a narrow ridge opposite each sepal and a large triangular bulge opposite each petal. Stamens arise as secondary primordia in alternating antesepalous and antepetalous cycles. Variation in number of stamens is due primarily to variation in the number of primordia that arise in the wider lower antepetalous loci. The primordium of the pistillode is girdling but becomes trilobed later. The gynoecium is initiated as three unequal crescentic carpel primordia that are united by zonal growth early in development. A procambial strand develops acropetally into each floral organ, and additional strands are formed as each organ increases in size. Floral organs are histologically specialized. The appearance of tannins, raphides, and silica and the maturation of sclerenchyma are basipetal within each floral organ.
AN ELECTROPHORETIC AND SEROLOGICAL INVESTIGATION OF SEED PROTEINS IN GALEOPSIS TETRAHIT L. (LABIATAE) AND ITS PUTATIVE PARENTAL SPECIES
Authors: Houts Karen Priddle , Hillebrand Gary R.
Published: January 2018

Seed proteins from the tetraploid Galeopsis tetrahit L. and its putative parental species G. pubescens Bess. and G. speciosa Mill., were examined using disc gel electrophoresis (PAGE), Ouchterlony double diffusion, and Immunoelectrophoresis. Forty‐three inbred cultivated lines of G. speciosa, G. pubescens, and G. tetrahit (both the naturally occurring species and an artificially produced hybrid) and two wild populations of G. tetrahit were examined. PAGE gels were stained for total protein or malate dehydrogenase. Although variability in the total protein pattern was detected within and between lines for all three species, there was much similarity among the taxa. No bands appeared in the hybrid that were not present in the parents. The band pattern for synthetic G. tetrahit was very similar to that of natural G. tetrahit suggesting that G. tetrahit originated from a cross in nature between G. pubescens and G. speciosa. The total protein PAGE results were analyzed using numerical taxonomic techniques. Although these analyses did not clearly separate the three species, the general tendency was toward grouping G. pubescens lines together, natural G. tetrahit lines together, and synthetic G. tetrahit lines together. Natural and synthetic G. tetrahit lines were also interspersed among each other along with some G. speciosa lines. The malate dehydrogenase pattern showed little variation among the three species. Qualitative serological methods did not distingush among the three species, but confirmed the similarity observed among the taxa in the results of electrophoresis.
GROWTH FORMS IN ARCTOSTAPHYLOS GLAUCA
Authors: Vasek Frank C. , Clovis Jesse F.
Published: January 2018

Arctostaphylos glauca has evolved two growth forms in the San Bernardino Mountains of Southern California. A chaparral ecotype of upright shrubs with relatively long leaves occurs in chaparral on the south and west sides of the mountain range. A desert woodland ecotype of low, compact, spreading shrubs with shorter leaves occurs in pinyon woodland on the north and northeast sides of the same range. The chaparral ecotype flowers early and fruits heavily. Upon periodic destruction by fire its populations are replaced by numerous seedlings. The woodland ecotype flowers late and fruits sparingly. Its lower seed reproductive potential is further indicated by the lower total number of floral units, by a lower proportion of fruit set, and by an apparent truncation of the flowering season before all the flower buds open. An alternative strategy, involving long life, compact growth form, and the exploitation of new soil resources by layering and vegetative reproduction in the absence of regular fire recycling has evidently adapted an old chaparral plant to recent desert woodland conditions.
DEVELOPMENT AND ORGANIZATION OF THE SECONDARY VESSEL SYSTEM IN POPULUS GRANDIDENTATA
Authors: Larson Philip R.
Published: January 2018

The apical 22 cm of a dormant, first‐year sprout of Populus grandidentata was sectioned serially, and the primary and secondary xylem systems were studied microscopically and graphically reconstructed. A total of 15 nodes was present on the mature stem and 14 foliar primordia in the dormant bud. The vascular traces in the lower portion of the mature stem conformed to a 2/5 phyllotaxy while those of the upper portion and within the dormant bud conformed to a 3/8 phyllotaxy. The 2/5 to 3/8 phyllotactic transition occurred in an extremely precise and systematic two‐step pattern: (1) The lateral traces shifted to a new point of origin on the parent central trace, and (2) three new central traces were initiated in sequence by divergences from left‐traces. Metaxylem, when followed downward, conformed to the arrangement of the procambial trace system only within one orthostichy. Below this point, the metaxylem components of lateral traces physically separated from those of the protoxylem and continued downward on a new course. Metaxylem vessels produced by the trace cambium originated from a postulated vessel‐generating center at the stem‐petiole junction. Each metaxylem vessel developing basipetally through the primary body was continuous with a secondary vessel developing basipetally in the secondary body. Because secondary development closed the vascular cylinder, vessels originating from developing leaves or primordia situated at higher levels in the shoot were displaced radially outward when they entered the secondary xyelm. The distribution of vessels in the secondary xylem can therefore be accounted for by a knowledge of the production and distribution of metaxylem vessels in the primary body.
PATTERNS OF MITOSIS AND DIFFERENTIATION IN CELLS DERIVED FROM PEA ROOT PROTOPLASTS
Authors: Landgren Craig R.
Published: January 2018

Mitotic figures of diploid, tetraploid, octaploid and 16‐ploid nuclei were observed in cultures of pea root protoplasts whose initial DNA content was apparently 2C and 4C. The distribution of these mitotic figures in the different ploidy levels paralleled the distribution of mitotic figures in the culture of intact root explants and may be related to the hormonal stimulation of mitoses in these cultures. The patterns of the time course of both DNA synthesis and cell division in the protoplast cultures were similar to such patterns observed in the culture of intact root explants, although longer lag periods were observed in the protoplast cultures. Mitotic abnormalities including both chromosome breakage and spindle disfunction were observed in protoplast cultures. A large portion of the cell pairs derived from mitoses (27 % in one experiment) contained Feulgen‐positive micronuclei. An accumulation of an as yet unidentified differentiation product termed dense cytoplasmic protoplast derivative was observed. Some of the conditions influencing the development of these derivatives are reported.
THE OCCURRENCE OF INTERCALARY AND UNINTERRUPTED MERISTEMS IN THE INTERNODES OF TROPICAL MONOCOTYLEDONS
Authors: Fisher Jack B. , French James C.
Published: January 2018

The distribution of percent of dividing nuclei, parenchyma cell length, total cell number per internode, and total internode length were determined for successive internodes in the apex and growing vegetative internodes of 23 tropical species in 17 families of monocotyledons. Basal intercalary meristems (IM) were found in representatives of Commelinaceae, Cyperaceae, Flagellariaceae, Poaceae, Restionaceae, and Marantaceae. Uninterrupted meristems (UM) which are confined progressively to the upper region of the internode and are not isolated meristematic regions were found in the Costaceae, Dioscoreaceae, Philesiaceae, Smilacaceae, Agavaceae, Araceae, Arecaceae, Liliaceae, Pandanaceae, and Zingiberaceae. Both IM and UM were found in different species of Orchidaceae. The only morphological trait correlated with meristem type was presence of sheathing leaf bases in all species with IM. Both IM and UM are interpreted as extensions of the primary elongating meristem; the IM is disjunct, and the UM is continuous with it. The phytomer growth unit and the presence of internodal IM's cannot be applied generally to the monocotyledons.
TRICHOMES OF CANNABIS SATIVA L. (CANNABACEAE)
Authors: Dayanandan P. , Kaufman Peter B.
Published: January 2018

The diversity of non‐glandular and glandular hairs of Cannabis sativa L. (marihuana) are described by scanning electron microscopy. The non‐glandular hairs are of two major types, as distinguished by size differences and locations, and all of them are highly silicified. The presence of silica as well as cystoliths of calcium carbonate help in the identification of marihuana even in its ash residues. X‐ray microanalyses of Cannabis hairs are compared with those of Humulus lupulus and Lantana camera, whose hairs have been considered to resemble those of marihuana. Glandular hairs are found to be of two major categories. One group consists of glands whose heads are generally made up of eight cells and the other group whose heads are generally made up of two cells but never more than four cells. All glands of both categories are stalked. Some glands of the first category are massively stalked and these are restricted solely to anthers and bracts of staminate and pistillate plants. The massive stalk is considered to be made up of epidermal and hypodermal cells that have grown in response to some stimulation during anthesis. Fine details of the shoot system of Cannabis, such as cuticular ridges on epidermal cells, warty protuberances on non‐glandular hairs, and surface views of glands in developing stages are also reported. Glandular hairs on the bracts of Humulus lupulus resemble those of Cannabis.
SHOOT APEX ORGANIZATION AND ORIGIN OF THE RHIZOME‐BORNE ROOTS AND THEIR ASSOCIATED GAPS IN DENNSTAEDTIA CICUTARIA
Authors: Stevenson Dennis Wm.
Published: January 2018

The shoot apex of Dennstaedtia cicutaria consists of three zones—a zone of surface initials, a zone of subsurface initials, and a cup‐shaped zone that is subdivided into a peripheral region and central region. A diffuse primary thickening meristem, which is continuous with the peripheral region of the cup‐shaped zone, gives rise to a broad cortex. The roots occurring on the rhizomes are initiated very near the shoot apex in the outer derivatives of the primary thickening meristem. The roots that occur on the leaf bases also differentiate from cortical cells. Eventually, those cortical cells situated between the newly formed root apical cell and the rhizome procambium (or leaf trace) differentiate into the procambium of the root trace, thus establishing procambial continuity with that of the rhizome or leaf trace. Parenchymatous root gaps are formed in the rhizome stele and leaf traces when a few of their procambial cells located directly above the juncture of the root trace procambium differentiate into parenchyma. As the rhizome procambium or leaf trace continues to elongate, the parenchyma cells of the gap randomly divide and enlarge, thus extending the gap.
THE FINE STRUCTURE OF SIEVE ELEMENTS OF NEREOCYSTIS LÜTKEANA
Authors: Schmitz K. , Srivastava L. M.
Published: January 2018

The sieve elements ofNereocystisfrom the base of phylloids contain numerous small vesicles, cytoplasm, ribosomes, and the usual organelles and membrane systems, including nuclei, plastids, mitochondria, dictyosomes, and endoplasmic reticulum. They have a thick secondary wall layer which is deposited along the longitudinal walls and at the sieve plate excluding the sieve pores. The sieve pores range in diameter from 100 to 400 nm and are lined by plasmalemma. The sieve elements from the hollow basal parts of the pneumatocyst show essentially the same features but have larger and fewer vesicles, relatively little cytoplasm, larger sieve pores, 400–900 nm in diameter, and may lack a nucleus. In old sieve elements there are large deposits of callose on the sieve plate and along the longitudinal wall; the vesicles seem to break down, and the protoplast appears necrotic. It is concluded that the trumpet hyphae and sieve tubes are basically the same type of cell, and that the trumpet‐shape of the sieve elements is due to their passive stretching during extension growth of the organ in which they occur. There are minor but significant differences among the sieve elements from different regions of the thallus which may reflect possible levels of structural specialization of the sieve elements within the same plant.
ACTION OF GIBBERELLIC ACID ON CELL PROLIFERATION IN THE SUBAPICAL SHOOT MERISTEM OF WATERMELON SEEDLINGS
Authors: Liu Peter B. W. , Loy J. Brent
Published: January 2018

Rates of cell proliferation were about 2.5 fold greater in gibberellic acid‐treated seedlings of dwarf watermelon than in untreated dwarf seedlings as determined by direct counts of pith cells in elongating hypocotyls of watermelon. The higher rates of cell proliferation observed in normal and GA‐treated dwarf seedlings were due both to shorter cell cycle times and increased growth fractions of cells than in dwarf seedlings. The shorter duration of the cell cycle in GA‐treated seedlings was primarily due to a reduced S period.
ENVIRONMENTAL AND HORMONAL CONTROL OF TURION GERMINATION IN MYRIOPHYLLUM VERTICILLATUM
Authors: Weber James A. , Noodén Larry D.
Published: January 2018

Germination, or outgrowth, of Myriophyllum verticillatum turions involves a series of visible changes starting with reflexing of leaves followed by extension and curving of the axis, and then by root formation. Before abscission, turions grow out in response to long days (16 hr) but not short days (8 hr). After abscission, turions show maximal dormancy which can be fully broken by a cold treatment (4 C). Turions are heterogeneous in degree of dormancy and ability to respond to less complete dormancy‐breaking treatments, e.g., long days at 20 C. Cytokinins (10‐6 m) break dormancy of non‐cold‐treated turions, whereas gibberellic acid (GA3) is ineffective except at high concentrations (10‐3 m). Continuous treatment with cytokinins causes abnormal development after germination. GA3, on the other hand, induces apparently normal development even at high concentration. Indoleacetic acid (IAA) induces outgrowth only at high concentrations (10‐3 ‐ 10‐4 m), but these concentrations also produce abnormal development. Abscisic acid (ABA, 10‐5 m) retards outgrowth of cold‐treated turions and can completely suppress it in non‐cold‐treated turions. The activity of ABA‐like substances in turions remains about the same before and during germination, whereas other (unidentified) acidic inhibitors decrease markedly. The cytokinin activity changes in a complex pattern.
MEASURING RATES OF SYMBIOTIC NITROGEN FIXATION BY ALNUS TENUIFOLIA
Authors: Fleschner Michael D. , Delwiche C. C. , Goldman Charles R.
Published: January 2018

Rates of nitrogen fixation were determined for alder (Abuts tenuifolia Nutt.) with the C2H2 assay and verified by the 15N method. Rates of C2H2 reduction obtained varied between 0.0342 and 10.9 μmoles per gram of nodule tissue (fresh weight) per hour with a seasonal average of 2.70 μmoles g‐1 hr‐1. Expressed as nitrogen fixation rates these are equivalent to 0.0114, 3.63, and 0.9 μmoles g‐1 hr‐1 of elemental nitrogen, respectively. Nitrogen fixation (15N) rates averaged 2.20 μmoles N g‐1 hr‐1 with a standard deviation of 1.14. The influence of pC2H2, pO2, temperature during incubation, length of incubation time, presence vs. absence of N2 in the incubation atmosphere, and amount of nodule biomass per sample were investigated.
THE EVOLUTION OF INSECT‐MEDIATED SELF‐POLLINATION FROM AN OUTCROSSING SYSTEM IN CALYPTRIDIUM (PORTULACACEAE)
Authors: Hinton W. Frederick
Published: January 2018

Calyptridium monospermum (Portulacaceae) comprises two biological races visited by different groups of insects. One race, pollinated by a bumblebee, Bombus vosnesenskii (Apidae), is outcrossing, while the other race is pollinated casually by a variety of other insects whose visits result in insect‐mediated self‐pollination and geitonogamy within the inflorescence. Insect‐mediated selfing is also the mode of pollination in the closely related species, C. umbellatum. While all plants of both species are self‐compatible, insect visitation is necessary for good seed set. Selfing populations of C. monospermum exhibit many floral adaptations for insect‐mediated self‐pollination which parallel those of the selfing C. umbellatum, while retaining vegetative characteristics typical of C. monospermum. These floral traits involve flower color and odor, style and stamen orientation, size of stigmatic surfaces, number of pollen grains produced, density of open flowers on inflorescences, and presence or absence of protogyny. Artifical pollination experiments show that these floral adaptations are effective in increasing the probability of insect‐mediated self‐pollination. Insect‐mediated selfing in C. umbellatum and in some populations of C. monospermum is encouraged and probably made necessary by the inconstant pollinating behavior of the insects which visit these plants, as shown by the large percentage of non‐Calyptridium pollen recovered from the bodies of insects captured while visiting these plants.
ULTRASTRUCTURAL FEATURES OF DEVELOPING SIEVE ELEMENTS IN LEMNA MINOR L.—THE PROTOPLAST
Authors: Melaragno Jerry E. , Walsh Michael A.
Published: January 2018

The occurrence and precise arrangement of phloem tissue is reported for the first time in the root of the duckweed, Lemna minor L. Since these plants are small enough to be prepared intact for electron microscopy, the induction of artifacts as a result of mechanical manipulation during specimen preparation is virtually eliminated. Ultrastructural features of the complete sequence of sieve‐element development are presented and are in some respects similar to what has been described in other monocotyledons (e.g., nuclear degeneration, aggregation of ER, elaboration of electron‐dense crystalline plastid inclusions). Mature sieve elements in Lemna are enucleate, lack P‐protein, contain a plasmalemma, ER‐aggregations, mitochondria, plastids and, in many instances, intact vacuoles. It is suggested that structural modification required for the sieve element to assume a transport function may not be very drastic, apart from the degeneration of the nucleus.
CYTOKININ‐ AND GIBBERELLIC ACID‐INDUCED EFFECTS ON THE STRUCTURE AND METABOLISM OF SHOOT APICAL MERISTEMS IN OPUNTIA POLYACANTHA (CACTACEAE)
Authors: Mauseth James D.
Published: January 2018

The dormant axillary buds of Opuntia polyacantha can be activated by either cytokinins or gibberellic acid. Under the influence of benzylaminopurine (BAP), the axillary bud meristem increases greatly in size and becomes mitotically active. The primordia produced by the meristem develop as normal photosynthetic leaves. Gibberellic acid (GA) also causes the meristem to become mitotically active, but the meristem does not increase in size. The primordia produced under the influence of GA develop as normal cactus spines. Leaf‐producing meristems and spine‐producing meristems have the same zonation, despite the differences in size. The meristems are composed of a uniseriate tunica, a central mother cell zone, peripheral zone, and a pith rib meristem. The mitotic activity of each of the zones in the leaf‐producing meristem differs significantly from the mitotic activity of the corresponding zones in the spine‐producing meristem.
THE SYSTEMATIC POSITION OF EOGINKGOITES
Authors: Ash Sidney R.
Published: January 2018

Eoginkgoites is a fan‐shaped, imparipinnate leaf with a short rachis and long petiole. It was first described from the Upper Triassic Newark Group of Pennsylvania by Bock who assigned the fossil to the Ginkgoales. The fossil has also been found in the Upper Triassic Chinle Formation in Utah and Arizona and in the Newark Group in North Carolina. Investigation of the well‐preserved specimens found in the Chinle Formation shows that the leaf has anastomosing venation, a marginal vein and paracytic (syndetocheilic) stomata. These characters indicate that the leaf is bennettitalean and Eoginkgoites is reassigned to the Bennettitales although its shape is perplexing. Eoginkgoites may be an important index fossil to the lower Upper Triassic (middle Carnian) rocks of North America.
MORPHOLOGY AND ANATOMY OF FLORAL AND EXTRAFLORAL NECTARIES IN CAMPSIS (BIGNONIACEAE)
Authors: Elias Thomas S. , Gelband Hellen
Published: January 2018

The genus Campsis (Bignoniaceae), with one New World and one Old World species, is unusual among temperate plants in having five distinct nectary sites. Multiple nectaries occur at all four of the extrafloral sites (petiole, calyx, corolla, fruit), representing an advanced strategy for ant attraction. The morphology and anatomy of the extrafloral nectaries in both species are uniform for the petioles, calyces, and young fruits; those on the outer corolla lobes are of slightly different forms. The generalized structure consists of one layer of basal cells, and a one‐ to two‐layered secretory cup. Because of their small size, there is no vascular tissue in them. The large, vascularized (phloem only) floral nectary is an annular structure subtending the ovary.
STARCH GRANULE (AMYLOPLAST) DEVELOPMENT IN ENDOSPERM OF SEVERAL ZEA MAYS L. GENOTYPES AFFECTING KERNEL POLYSACCHARIDES
Authors: Boyer C. D. , Daniels R. R. , Shannon J. C.
Published: January 2018

Endosperm cell and starch granule (amyloplast) development of six maize (Zea mays L.) genotypes, normal, amylose‐extender (ae), sugary (su), waxy (wx), amylose‐extender sugary (ae su), and amylose‐extender waxy (ae wx), was compared. Endosperms of all genotypes were indistinguishable at 14 days after pollination. Cells were highly vacuolated and those in the central crown area of the kernel contained small starch granules in close association with the nucleus. Cellular and nuclear enlargement occurred during endosperm development in all genotypes, and major and minor gradients in physiological age of endosperm cells were observed in all kernels. Amyloplast development varied with genotype. Plastid development in normal and wx cells was characterized by an initial starch granule formation followed by granule enlargement to cell maturity. Endosperms homozygous for ae (ae, ae su, and ae wx) developed abnormal plastid‐granules. Secondary granule formations preceded development of abnormality in ae and ae su, but not in ae wx endosperms. In contrast to ae and ae su starch granules, ae wx granules were highly birefringent indicating a high degree of crystallinity. In all three ae genotypes, abnormality increased as a function of kernel and physiological cell age. The su mutant had two distinct effects on amyloplast development. First, a mobilization of the initially formed starch, and second a synthesis and accumulation of phytoglycogen and the formation of large rounded plastids. In ae su plastid development, there was a mobilization of the starch initially formed (resulting in irregularly shaped, nonbirefringent granules) but only small amounts of phytoglycogen were produced.
TIME‐LAPSE PHOTOGRAPHIC OBSERVATIONS OF MORPHOGENESIS IN ROOT NODULES OF COMPTONIA PEREGRINA (MYRICACEAE)
Authors: Bowes Bryan , Callaham Dale , Torrey John G.
Published: January 2018

Seedlings of the sweet fern Comptonia peregrina (L.) Coult. were grown aeroponically with their roots bathed in a nutrient mist lacking nitrogen except for 10 ppm N at the outset. The initiation and early development of root nodules capable of fixing atmospheric nitrogen were recorded with time‐lapse photography through early development to the establishment of highly branched, roughly spherical nodules. In Comptonia multiple primary nodule lobes are formed at or near the site of infection with as many as 10 primary lobes occurring together. On the shoulders of the swollen primary lobes new primordia develop, forming secondary nodule lobes, which may persist without nodule root elongation, giving a coralloid appearance. The tips of the lobes may elongate, forming nodule roots which grow vertically upward, or, if disturbed, in random orientation. Nodule roots occasionally form lateral roots. The root axis upon which the nodule forms undergoes secondary thickening on the proximal side of the nodule attachment; the distal portion of the root shows no secondary thickening and later atrophies. Thus, nodules are perennial structures on a woody root system. The endophyte infects and occupies the basal cortical tissues of the primary nodule lobes and successive nodule lobes as they are formed, being restricted to the swollen bases and not infecting the elongate nodule roots. Development of the nodule is interpreted in terms of complex host‐endophyte interactions involving the initiation of multiple primordia forming nodule lobes, the active inhibition of nodule lobes and finally nodule root elongation. Anatomical evidence for the endogenous origin of nodule primordium formation substantiates the view obtained from time‐lapse photomacrography.
A CYTOLOGICAL CONSPECTUS OF THE GENUS CALYCADENIA (ASTERACEAE): AN EXAMPLE OF CONTRASTING MODES OF EVOLUTION
Authors: Carr Gerald D.
Published: January 2018

The chromosome numbers of 12 taxa of Calycadenia are documented by determinations in 77 widespread populations of the genus. Results of biosystematic studies indicate that hybrids among C. multiglandulosa, C. ciliosa, C. pauciflora, C. hispida, C. spicata, and C. oppositifolia characteristically have multiple associations of chromosomes producing complex meiotic configurations, whereas hybrids among C. villosa, C. mollis, C. truncata, and C. tenella generally yield few or no bivalents and a predominance of univalents during meiosis. Hybrids between C. multiglandulosa and C. hispida exhibit strict bivalent pairing and high pollen stainability. It is demonstrated that C. pauciflora and C. ciliosa comprise several sibling taxa that are morphologically cryptic, yet highly differentiated cytologically. Conversely, it is concluded that C. multiglandulosa and C. hispida comprise at least five morphologically distinct taxa that so far as known are highly interfertile (as judged by pollen stainability of hybrids) and cytologically uniform. Reproductive biology, chromosome mutation rates, habitats, flowering time, and genetic recombination mechanisms of the C. pauciflora‐C. ciliosa and C. multiglandulosa‐C. hispida complexes are compared in an attempt to account for the different modes of evolution observed in these closely related groups of Calycadenia. Lacking other plausible explanations, it is suggested that differential methods for limiting recombination of critical adaptive gene complexes might account for the divergent evolutionary patterns encountered in Calycadenia.
THE EFFECT OF BORON DEFICIENCY ON CALLOSE FORMATION AND 14C TRANSLOCATION IN BEAN (PHASEOLUS VULGARIS L.) AND COTTON (GOSSYPIUM HIRSUTUM L.)
Authors: van de Venter H. A. , Currier H. B.
Published: January 2018

Callose accumulated in the tissues of boron deficient bean and cotton plants, the extent and distribution of which depended on the species. Sieve plates in the phloem of boron deficient bean were characterized by heavy plugs of callose, while the sieve plates of boron deficient cotton were essentially unaffected. Translocation of 14C was, however, drastically reduced in both plants. It is suggested that callose deposition in boron deficient plants is a secondary effect of cellular damage.
PREY CAPTURE AND FACTORS CONTROLLING TRAP NARROWING IN DIONAEA (DROSERACEAE)
Authors: Lichtner F. T. , Williams S. E.
Published: January 2018

Traps of Dionaea which have captured prey by a rapid closure mechanism continue to close with the lobes of the trap assuming a tightly appressed condition called the narrowed phase. Traps fed ants, which make up about one‐third of the prey captured in the field, assumed the narrowed condition within about 7 h of feeding. Ants were alive and capable of delivering mechanical stimulation to the trigger hairs until about 8 h after feeding when they were apparently killed by acid fluid (pH 2–3) secreted by the trap at that time. That stimulation of trigger hairs delivered by the insect during this period is sufficient to cause both the narrowing and acid secretion was demonstrated by laboratory experiments in which both of these responses were initiated within 5 h by stroking the trigger hairs with clean, dry nylon bristles. Such purely mechanical stimuli, delivered to the trigger hairs, produced action potentials in the trap throughout the period of stimulation. Chemicals such as Na+, NH4+, urea, and amino acids were capable of producing the narrowing response within one or two days. There was a 50% response to NaCl and NH4Cl solutions of about 6 mM and a 90% response to 34 mm solutions. Urea, L‐lysine, and glycine produce a significant response at 50 mm but can cause necrosis of the trap tissue at concentrations above 50 mm. Salt‐free ovalbumen (0.5 and 5.0 g/l) and KCl, CaCl2, and D‐glucose were ineffective in initiating the narrowing response. The level of Na+, NH4+, and amino acids necessary to elicit the narrowing response is within the range of concentrations previously demonstrated to exist in the haemolymph and tissues of prey known to be captured by Dionaea in the field. The data is consistent with the hypothesis that narrowing and secretion are initiated by mechanical stimulation and maintained by chemical stimulation after the death of the prey.
EFFECT OF BUFFERED SOLUTIONS AND SULFATE ON VEGETATIVE AND SEXUAL DEVELOPMENT IN GAMETOPHYTES OF PTERIDIUM AQUILINUM
Authors: Evans Lance S. , Bozzone Donna M.
Published: January 2018

Experiments were performed to determine effects of buffered solutions (0.01 m) on vegetative development and fertilization of gametophytes of Pteridium aquilinum. Buffered solutions were used to simulate exposures to acidic precipitation up to 3.5 h. Flagellar movement of sperm was reduced at buffer pH levels below 5.8. Specifically, longevity of motility was reduced so that no movements were observed 8–10 and 5–7 min after exposure to pH 5.6 and 5.2, respectively. Addition of sulfate (86 μm) depressed the percent motile sperm by 50%, 2–4 min after exposure at all pH values tested. Longevity of flagellar movement was most affected by pH and additions of sulfate. The effect on fertilization was assayed directly by determinations of sporophyte production. Although gametophyte survival and development were not affected by solutions of pH 5.8 to 2.2, fertilization was reduced after exposure to buffers below pH 4.2. Sporophyte production was not altered at pH 5.2 but was reduced 50% at pH levels of 4.2 and 3.2 compared with exposures to pH 5.8. Addition of sulfate (86 μm) decreased fertilization at least 50% at all pH levels observed. The results suggest that only limited fertilization, and therefore limited genetic recombinations could occur in Pteridium aquilinum under conditions of acidic precipitation (pH and sulfate levels) that prevail in the northeastern United States.
DEVELOPMENT AND STRUCTURE OF THE VASCULAR CONNECTION BETWEEN THE PRIMARY AND SECONDARY ROOT OF GLYCINE MAX (L.) MERR.
Authors: Byrne John M. , Pesacreta Thomas C. , Fox Joseph A.
Published: January 2018

The primary vascular connection between primary and secondary root of Glycine max (L.) Merr. was derived from stelar parenchyma and pericycle. Inner stelar parenchyma, associated with the parent metaxylem and outer stelar parenchyma adjacent to the pericycle, were resonsible for the histogenesis of the primary xylem connection. Acropetal maturation of the diarch xylem connection occurred after the lateral root emerged from the parent root. Development of tetrarchy occurred distal to the diarch xylem connection. The concentric primary phloem connection was derived from the pericycle and outer stelar parenchyma. Acropetal maturation of the primary phloem connection occurred prior to lateral root emergence from the parent root. Secondary growth quickly augmented the primary vascular connection. A substantial amount of mature secondary xylem formed prior to maturation of the secondary phloem. The structure of the primary and secondary vascular connections is described.
A SYSTEMATIC STUDY OF PENNISETUM SECT. PENNISETUM (GRAMINEAE)
Authors: Brunken Jere N.
Published: January 2018

Pennisetum sect. Pennisetum includes two reproductively isolated species. Pennisetum purpureum Schumach. is a tetraploid (2n = 28) perennial species which occurs throughout the wet tropics of the world. Pennisetum americanum (L.) Leeke is a diploid (2n = 14) annual species, native to the semi‐arid tropics of Africa and India, and contains three morphologically diverse subspecies. Subspecies americanum includes the wide array of cultivated pearl millets. Subspecies monodii from the Sahel of West Africa is identified as the wild progenitor of pearl millet. Subspecies stenostachyum is morphologically intermediate between subsp. americanum and monodii and includes the mimetic weeds often associated with the cultivation of pearl millet.
FERAXOTHECA GEN. N., A LYGINOPTERID POLLEN ORGAN FROM THE PENNSYLVANIAN OF NORTH AMERICA
Authors: Millay Michael A. , Taylor Thomas N.
Published: January 2018

The pollen organ Feraxotheca gen. n. is described from Pennsylvanian age coal balls from the Lewis Creek, Kentucky, locality. The fructifications consist of bilaterally symmetrical synangia composed of a basal pad supporting elongate sporangia that are laterally appressed for the entire length of the sporangial cavities. Sporangial tips extend over the center of the synangium and delimit a small open area, while the bases arise from a parenchymatous cushion that is bounded by short tracheid‐like cells. Each synangium is borne on the surface of an expanded pinna tip and is surrounded by a small amount of laminar tissue that envelopes the base of the synangium. Ultimate pinnae are rectangular in transverse section, possess an elliptical vascular bundle surrounded by canals containing a yellow froth‐like substance, and have a cortex of elongate cells that radiate from the center of the axis. Sporangia contain small (40–64 μm), radial, trilete spores ornamented by regularly spaced coni or blunt tipped grana. Feraxotheca is compared with the compression genus Crossotheca and some new ideas are advanced concerning the morphology of this compression genus. The obvious differences between Feraxotheca and other lyginopterid pollen organs strongly suggests that the Lyginopteridaceae, as it is currently interpreted, is an unnatural family.
TISSUE ELECTROPOTENTIALS IN KALANCHOË BLOSSFELDIANA DURING WOUND HEALING
Authors: Gensler W.
Published: January 2018

Penetrating palladium probes were placed in the stem and leaf of Kalancho'ë blossfeldiana. The electropotentials arising in the probes at the wound site were continuously monitored during the subsequent healing process. The potential change was always in the positive going direction, beginning at an average of 320 millivolts and stabilizing at an average of 601 millivolts relative to a standard hydrogen electrode. The healing process can be divided into two distinct phases: an initial phase of approximately 6 hr duration in which the potential rises rapidly and a second phase extending to approximately dusk on the third day in which the potential rises at a substantially lower rate. There is also a definite change of the transition potential waveshape at the beginning and end of the 16‐hr light period during the healing process. Rewounding results in a potential recovery waveshape similar to the original healing response but of shorter duration. The data are interpreted in terms of the redox status of the wound site.
THE STRUCTURE OF THE ACERVULUS, THE FLOWER CLUSTER OF CHAMAEDOREOID PALMS
Authors: Uhl Natalie W. , Moore Harold E.
Published: January 2018

Developmental evidence shows that the acervulus, a distinctive flower cluster found only in the chamaedoreoid group of palms, is a form of cincinnus. In Hyophorbe indica Gaertner, the unit consists of a row of sessile flowers, the upper 3–4, staminate and the basal flower, pistillate. During initiation, each new flower originates from divisions in the T2 and underlying layers of the lower right or left flank of the apex of the preceding flower. A bract subtending the first flower is evident in early stages, is displaced basipetally as the flowers are formed, but is obscured when flowers are mature. No other bracts are associated with the unit. One to two outer bundles of the vascular cylinder of the rachilla develop first to the uppermost flower. Subsequently, bundles to other flowers arise as lower branches of the first bundle and from other, often small outer bundles of the rachilla that become floral traces or produce one or more branches to a flower. Many of the bundles supplying the flowers bend sharply downward in the cortex of the rachilla, apparently reflecting the basipetal sequence of floral inception.
MINERAL DISTRIBUTION IN RELATION TO FRUIT DEVELOPMENT AND MONOCARPIC SENESCENCE IN ANOKA SOYBEANS
Authors: Derman Belma D. , Rupp David C. , Noodén Larry D.
Published: January 2018

The changes in distribution of several important mineral nutrients (N, K, Ca, Mg, Mn, and Fe) were studied in relation to monocarpic senescence (measured as leaf yellowing) and fruit development in hydroponically‐grown (and to a lesser extent field‐grown) Anoka soybeans with particular emphasis on the leaves and seeds. Only N shows a clear redistribution from the leaves to the seeds as the seeds grow, and this transfer starts before visible leaf yellowing. K, Ca, Mn and Fe do not seem to redistribute, but Mg may undergo limited redistribution. Depodding prevents the drop in the amounts of minerals in attached leaves by blocking leaf shedding and/or redistribution and also creates some quantitative changes in mineral distribution. On a g fresh weight basis, only the N content of leaf blades decreases during yellowing; the K, Mg, Ca, Mn and Fe contents do not decrease. Therefore, depletion of the latter minerals from the leaves cannot be responsible for their yellowing. Although N deficiency alone could cause foliar chlorosis, the monocarpic yellowing pattern is distinctly different from that induced by N deprivation.
LEAVES OF ARCHAEOSIGILLARIA VANUXEMII, A DEVONIAN LYCOPOD FROM NEW YORK
Authors: Fairon‐Demaret Muriel , Banks Harlan P.
Published: January 2018

The leaf of mid Devonian Archaeosigillaria vanuxemii from Gilboa, N.Y. is known to have a thick conical base. This study demonstrates by the uncovering technique the attachment of leaves to the stem, the flattened lamina that is deltoid in outline with a toothed margin, and an apex prolonged into a hair. Comparisons are made with specimens from Kazakhstan. The morphology of leaves of other species of Archaeosigillaria and the slowly accumulating data on leaves of Devonian lycopods are discussed.
ZINC AND COPPER TOLERANCE OF AGROSTIS STOLONIFERA L. IN TISSUE CULTURE
Authors: Wu Lin , Antonovics Janis
Published: January 2018

Callus tissue was induced from shoot meristematic tissue and root tips of a clone of the grass Agrostis stolonifera tolerant to both zinc and copper, and from a control clone tolerant to neither metal. Growth of the callus tissue on media containing zinc and copper showed that tolerance to both metals was maintained in tissue culture. The pattern of metal uptake in tissue culture resembled uptake by whole plants in that tolerant tissue took up more metal than nontolerant tissue. Plants regenerated from callus had the same copper and zinc tolerance as the original parental clones regardless of time of growth in tissue culture and shoot or root origin of the tissue. The results support previous evidence that metal tolerance is genetically determined and acts at the cellular level.
BREEDING SYSTEM IN LIMNANTHES ALBA: SEVERAL ALTERNATIVE MEASURES
Authors: Jain S. K.
Published: January 2018

Seven populations of Limnanthes alba were described for their rates of outbreeding, amount of genetic variability, and response to enforced selfing in terms of inbreeding depression. Outcrossing rates, estimated by using two genetic marker loci, varied between 43 and 97%. Heterozygosity level was found to be in the range of 12 and 27 percent, whereas percent polymorphic loci varied twofold (between 29 and 57%) among populations. Inbreeding depression was found to be significant in four of seven populations for number of flowers per plant, plant height, and seed set per flower. There was no association between observed patterns of inbreeding response and predictions from the genetic variation parameters, so that variations in outbreeding rates and consequences need a detailed quantitative verification. In populations showing no inbreeding depression, autofertility seemed to increase with inbreeding (presumably accompanied by natural selection) and to be under genetic control. This is relevant to the hypothesis on the origin of inbreeders under conditions lacking pollinators, e.g., colonization of marginal areas.
FASCIATION AND DICHOTOMOUS BRANCHING IN ECHINOCEREUS (CACTACEAE)
Authors: Boke Norman H. , Ross Robert G.
Published: January 2018

In Echinocereus reichenbachii dichotomous branching and fasciation (cresting) are rare events. Both were found together in only a few of many populations investigated and are interpreted as variants of a single phenomenon. They may occur at any stage of shoot development, but crest meristems arise most commonly on young branches among clusters of normal shoots. Sometimes they appear on unbranched young plants or seedlings, very rarely on older shoots. Dichotomy results from the division of an apical meristem into equal parts each of which functions independently, producing a forked shoot. Fasciation involves the extension of a single meristem into an apical ridge. The product is a flabellate shoot that becomes undulate if growth along the summit continues. In longisection linear meristems appear similar to radial sections of normal shoots; in median sagittal section they have a much extended central mother cell zone within which the cell pattern resembles a rib meristem. Although crest meristems become sluggish or even inactive with age, localized renewed growth may occur spontaneously or be induced by injury. In this species the random production of normal shoots from crest meristems (defasciation) was not observed, but if much or all of such a meristem is removed, branches may arise from lateral areoles, and these are always normal. It seems, therefore, that whatever induces fasciation in E. reichenbachii originates in and is restricted to the apical meristem and its immediate vicinity.
COMPARATIVE POLLINATION ECOLOGY OF PYRRHOPAPPUS GEISERI AND PYRRHOPAPPUS CAROLINIANUS
Authors: Barber Susan C. , Estes James R.
Published: January 2018

Pyrrhopappus geiseri and P. carolinianus are partially cross‐compatible (20–52% akene set in artificial crosses). Four barriers to gene exchange prevent or reduce hybridization. Pyrrhopappus geiseri flowers in the early spring, whereas P. carolinianus flowers from mid‐spring to summer with peak flowering in May and June. Overlap in anthesis between the two species is therefore limited. The two species typically occupy different soil‐types, P. geiseri on clay soils and P. carolinianus on sands. The diurnal periods of stigmatic receptivity are distinct. Pyrrhopappus geiseri is pollen receptive in the late morning and P. carolinianus at dawn. As a result of the prior three barriers P. geiseri is pollinated by bees of the Andrena verecunda complex, primarily A. crawfordi, and P. carolinianus by Hemihalictus lustrans. Pyrrhopappus geiseri and P. carolinianus are almost completely reproductively and ecologically isolated and are not members of one hologamodeme.
PHENOTYPIC PLASTICITY IN DRAPARNALDIA (CHAETOPHORACEAE). II. THE PHYSICAL ENVIRONMENT AND CONCLUSIONS
Authors: Johnstone I. M.
Published: January 2018

Eight isolates of Draparnaldia from a variety of freshwater habitats were grown in unialgal, defined culture. The morphological responses of these isolates to different daylengths, light intensities and temperatures are described. The phenotypic expression of Draparnaldia is markedly modified by all three factors. The interaction of these environmental variables was highly significant, and it is not possible, in most cases, to describe or predict the morphological appearance of Draparnaldia by referring to one of these parameters in isolation. The adaptive significance of phenotypic plasticity in Draparnaldia is discussed.
ULTRASTRUCTURE OF THE MATURE UNGERMINATED RICE (ORYZA SATIVA) CARYOPSIS. THE STARCHY ENDOSPERM
Authors: Bechtel Donald B. , Pomeranz Yeshajahu
Published: January 2018

The structure of the starchy endosperm of rice (Oryza sativa) was studied by using light and transmission electron microscopy coupled with proteolytic enzyme digestions. The starchy endosperm was divided into two regions, the subaleurone and central, based on the number and types of protein bodies observed. The subaleurone region contained three different types of membrane bounded protein bodies—large spherical, small spherical, and crystalline protein bodies. The small spherical protein bodies were most numerous and the large spherical ones were least numerous. The crystalline protein bodies displayed crystal lattice fringes and were a composite of smaller angular components. The central region lacked both the small spherical and crystalline protein bodies. The large spherical protein bodies of this region were located in pockets of densely stained proteinaceous material. In contrast to the relatively well preserved cytoplasm of the subaleurone region, the central endosperm zone consistently was poorly preserved.
THE GERMINATION STRATEGY OF OLDFIELD ASTER (ASTER PILOSUS)
Authors: Baskin Jerry M. , Baskin Carol C.
Published: January 2018

At maturity in November, a high percentage of Aster pilosus Willd. seeds germinated in light at high temperatures (30/15, 35/20 and 40/25 C). Stratification during winter lowered the temperature requirement for germination, and high percentages of germination were obtained in light at 15/6 and 20/10 C., as well as at 30/15, 35/20 and 40/25 C. Stratification in darkness was completely ineffective, but stratification in light was partially effective in overcoming the light requirement for germination. Inability of seeds to germinate at low temperatures prevents germination after dispersal in late autumn and winter, when freezing temperatures could kill the seedlings. The lowering of the temperature requirement for germination during winter stratification allows the seeds to germinate and the resulting vegetative rosettes to become well established before the onset of the periodic summer droughts that occur in habitats occupied by A. pilosus.