bluuebunny/crossref_metadata_2025 huggingface dataset:
GERMINATION OF LIGHT‐INHIBITED SEED OF NEMOPHILA INSIGNIS
Authors: Chen Shepley S. C.
Published: January 2018

Germination of Nemophila insignis seed is inhibited by light over a wide range of temperatures. At low temperatures the light intensity required for inhibition is higher. At 25 C there is little germination (in darkness as well as in light); at 27.5 C germination is inhibited altogether. Virtually complete germination in light is obtained when the endosperm directly covering the radicle is removed. This operation also improves germination in darkness at 25 C. Mechanical scarification performed elsewhere in the seed is without effect. As with Phacelia tanacetifolia, Nemophila seed apparently fails to germinate in light because the endosperm restrains the expansive growth of the embryo. The embryo of dark‐imbibed seed develops a force which enables it to overcome the physical resistance of the endosperm. Light inhibits the process which leads to generation of “expansive force.” Gibberellic acid at 5 × 10–4 m stimulates germination in light and in the dark. Abscisic acid at 10‐4 m inhibits germination; at 10‐6 m it inhibits only root growth. The inhibition of germination or root growth caused by abscisic acid cannot be reversed by gibberellic acid. Eighty per cent oxygen under certain conditions promotes germination. The rate of O2 uptake is enhanced in oxygen‐enriched atmosphere; however, there is no corresponding increase in the rate of CO2 output. Thus high oxygen tension enhances an oxidative process other than respiration. This reaction is favorable to seed germination.
ULTRASTRUCTURE OF CHLOROPLASTS AND CHROMOPLASTS IN CAPSICUM ANNUUM I. THYLAKOID MEMBRANE CHANGES DURING FRUIT RIPENING
Authors: Spurr Arthur R. , Harris William M.
Published: January 2018

Developing chromoplasts in the fruit of Capsicum annuum were examined by electron microscopy. Special attention was given to changes in the thylakoid system. All grana and some intergranal thylakoids in the mature chromoplasts of the seven cultivars studied underwent lysis. The particulate nature of the granal membranes disappeared during lysis before the relationship between the partitions and locules was obscured. The changes during lysis support the globular concept of membrane structure. The selective lysis of the synaptic membranes of the granal partitions may be attributed to their distinctive composition and structure. Lipid globules (osmio‐philic) did not accumulate in the immediate region of granal lysis, indicating that they are not directly derived from membranes undergoing degradation. During and following granal lysis a profuse development of intergranal thylakoid membranes occurred in several cultivars. In some instances a thylakoid plexus (prolamellar body) was formed. This specialized structure of the thylakoid system occurs in the chromoplasts of other species as well as in other types of plastids. Extensive, concentrically arranged thylakoid sheets with specific interspaced membrane relationships were frequently associated with the plexus. Several types of membrane associations and interrelationships in the plastid are described. An analysis of one type of membrane configuration, the thylakoid sheets, indicated that one method of growth may be through intussusception into the original membrane. The development of thylakoid plexes and of extensive thylakoid sheets during or after granal lysis indicates that dynamic synthetic activities occur in the chromoplasts of some cultivars of pepper during fruit ripening.
POLLEN TUBE GROWTH AND INCOMPATIBILITY FOLLOWING INTRA‐ AND INTER‐SPECIFIC POLLINATIONS IN LILIUM LONGIFLORUM
Authors: Ascher Peter D. , Peloquin S. J.
Published: January 2018

The growth of pollen tubes of a sampling of Lilium species in styles of L. longiflorum incubated at 24 C for 48 hr after pollination indicated two types of interspecific incompatibility. Pollen tubes of two self‐compatible species of section Leucolirion, the section including L. longiflorum, stopped growth abruptly upon reaching the stylar canal, were of abnormal morphology, and were incapable of continued growth with longer incubation. Pollen tubes of self‐compatible or self‐incompatible species of sections Sinomartagon, Pseudolirium, Liriotypus, and Daurolirion approached but did not exceed the length of intraspecific incompatible pollen tubes in styles of L. longiflorum. Pollen tube morphology was normal and tubes were capable of continued growth with additional incubation. Unilateral interspecific incompatibility occurred in reciprocal crosses between self‐incompatible L. longiflorum and self‐compatible L. regale and L. formosanum, but exceptions occurred in Aurelian hybrids. Incubation of interspecifically pollinated L. longiflorum styles at 39 C, which removes the self‐incompatibility reaction, had no effect on interspecific incompatibility.
BIOSYSTEMATICS OF THE BOTHRIOCHLOA BARBINODIS COMPLEX (GRAMINEAE)
Authors: de Wet J. M. J.
Published: January 2018

The New World species of Bothriochloa O. Kuntze are polyploids with 2n = 60, 120, 180 and 220 chromosomes and they reproduce sexually. Plants with 2n = 180 chromosomes constitute the extremely variable B. barbinodis (Lag.) Herter, which is subdivided into var. barbinodis, var. palmeri (Hack.) de Wet comb. nov., and var. schlumbergeri (Fourn.) de Wet comb. nov. The single collection with 2n = 220 chromosomes belongs with var. schlumbergeri. Plants resembling B. barbinodis in inflorescence structure but having well‐developed pedicellate spikelets and 2n = 120 chromosomes are included in B. campii (Swallen) de Wet comb. nov. South American collections of B. springfieldii (Gould) Parodi differ from North American collections in having 2n = 60 rather than 120 chromosomes and in having larger inflorescences as does B. barbinodis. Variety australis de Wet. var. nov. is described to include them.
STRUCTURE AND DEVELOPMENT OF THE FLOWER AND FRUIT OF PERESKIA DIAZ‐ROMEROANA
Authors: Boke Norman H.
Published: January 2018

Pereskia diaz‐romeroana and its putative relatives are scandent plants with vigorously growing long shoots, small flowers and fruits, and tuberous root systems. Except for size, floral development parallels that in other pereskias. The gynoecium has three to six carpels, is basically superior with axlie placentation, and is partially divided into locules by the connate carpel margins. The closest relative of these Andean forms appears to be P. aculeata.
INDUCED DIFFERENTIATION OF GERANIUM PLANTS FROM UNDIFFERENTIATED CALLUS IN VITRO
Authors: Pillai S. K. , Hildebrandt A. C.
Published: January 2018

Geranium callus produced from explants of stem tip, internode pith with vascular tissue on synthetic media with or without coconut milk and 2,4‐dichlorophenoxyacetic acid grew well for many generations, but only tracheids were induced in them. If callus produced on these media was subcultured immediately on Murashige and Skoog medium with 0.1 mg/liter/α‐naphthalene acetic acid (NAA) and 10.0 mg/liter kinetin (K) and incubated at 16/8‐hr light/dark cycle, shoots were induced in 8‐10 weeks and roots in another 8‐10 weeks. Callus produced on the MS medium with the same supplements of NAA and K, subcultured on the same medium and incubated in 16/8‐hr light/dark cycle, produced shoots in 6‐8 weeks. However, on callus subcultured more than three times, shoots differentiated with greater difficulty and none differentiated after six subcultures. Some abnormal shoot‐like structures were also produced, the cells of which showed virus‐like inclusion bodies. Requirements of the different varieties for differentiating organs differed. Among 12/12‐, 15/9‐, 16/8‐, and 20/4‐hr light/dark photoperiods that induced differentiation, 15/9‐ and 16/8‐hr were more effective than the others. Continuous illumination did not induce differentiation. Differentiated shoots formed roots more readily on a medium with reversed proportions of auxin and kinetin. On agar roots were devoid of root hairs. Root hairs were formed when the shoots and plantlets were cultured on filter‐paper bridges. Many “mother” stock plants were produced. These are being studied for their growth qualities and for possible viruses and other pathogens.
DEVELOPMENT OF THE DIMORPHIC CHLOROPLASTS OF SUGAR CANE
Authors: Laetsch W. M. , Price Ian
Published: January 2018

The vascular bundle sheath cells of sugar cane contain starch‐storing chloroplasts lacking grana, whereas the adjacent mesophyll cells contain chloroplasts which store very little starch and possess abundant grana. This study was undertaken to determine the ontogeny of these dimorphic chloroplasts. Proplastids in the two cell types in the meristematic region of light‐grown leaves cannot be distinguished morphologically. Bundle sheath cell chloroplasts in tissue with 50% of its future chlorophyll possess grana consisting of 2‐8 thylakoids/granum. Mesophyll cell chloroplasts of the same age have better developed grana and large, well structured prolamellar bodies. A few grana are still present in bundle sheath cell chloroplasts when the leaf tissue has 75% of its eventual chlorophyll, and prolamellar bodies are also found in mesophyll cell chloroplasts at this stage. The two cell layers in mature dark‐grown leaves contain morphologically distinct etio‐plasts. The response of these two plastids to light treatment also differs. Plastids in tissue treated with light for short periods exhibit protrusions resembling mitochondria. Plastids in bundle sheath cells of dark‐grown leaves do not go through a grana‐forming stage. It is concluded that the structure of the specialized chloroplasts in bundle sheath cells of sugar cane is a result of reduction, and that the development of chloroplast dimorphism is related in some way to leaf cell differentiation.
FINE STRUCTURE CHANGES DURING FUNCTION OF THE DIGESTIVE GLAND OF VENUS'S‐FLYTRAP
Authors: Schwab D. W. , Simmons E. , Scala J.
Published: January 2018

Changes in the structure of the digestive gland cells of Venus's‐flytrap during the digestive process have been studied with light and electron microscopy. Large vacuolar lipid‐protein inclusions break up and become smaller; however, they never completely disappear during the entire 7‐10‐day cycle. Dictyosomes in the resting digestive gland are associated with small, inconspicuous vesicles, whereas during the digestive cycle two types of prominent vesicles are observed on the peripheral tubules. Changes in plastid fine structure are complex and involve the disappearance of lipid globules and the tubular complex, followed by the formation of microtubules on the thylakoids and cisternae on the outer plastid membrane. Mitochondrial fine structure changes from the small cristae and light matrix of the resting state to large cristae and a very dense matrix representative of a change to a state where phosphorylation is tightly coupled to electron transport. Pronounced changes which occur in the cell envelope (cell wall and membrane taken together) are apparently associated with secretion of the digestive fluid. Numerous other changes are observed such as polysome formation, multivesicular body formation, mitochondria division, and changes which can be attributed in general to elevated cell activity.
ULTRASTRUCTURAL CHANGES IN DIRECTLY GERMINATING SPORANGIA OF PHYTOPHTHORA PARASITICA
Authors: Hemmes Don E. , Hohl Hans R.
Published: January 2018

Flagella and cleavage vesicles form during the initial stages of direct germination in the same manner as they do in indirect germination. Later, however, the flagella degenerate and cleavage of the cytoplasm is not complete. Instead, a new wall layer is deposited onto the existing sporangial wall, and this germination wall extends with the germ tube and forms the hyphal wall. Material for the germination wall first appears around vesicular aggregates concentrated at the periphery of the sporangial cytoplasm. As the wall forms the vesicular aggregates become encased in it, and the wall eventually consists of irregular deposits of wall material interspersed with the vesicular aggregates. These are clearly cytoplasmic in nature and different from lomasomes, since they are associated with ribosomes and other small elements of the cytoplasm. Likely to contribute to the wall formation are the endoplasmic reticulum, microbodies, dictyosome‐derived vesicles, and possibly polyvesicular bodies and larger vacuoles with fibrillar contents. The basal plug of the sporangium forms the same way as the germination wall and also contains numerous vesicular inclusions. Fewer vesicular inclusions are found in the sporangial wall, and none have been observed in the walls of the growing hyphae. This difference in wall structure can be explained on the basis of their different growth patterns. Penetration of the sporangial plug is concomitant with prominent lomasomal activity and the cytoplasm at the hyphal tip is characterized by the presence of numerous vesicles, which are probably derived from dictyosomes.
THE GENUS PELECYPHORA (CACTACEAE): RESOLUTION OF A CONTROVERSY
Authors: Anderson Edward F. , Boke Norman H.
Published: January 2018

The four species considered in this article fall into two natural groups. The evidence presented for this conclusion involves not only external features such as floral, fruit, and seed morphology, but also that obtained from internal structure, including tubercle and areole development, the anatomy of surface layers of mature tubercles, the structure of crystals in the ground tissues, and features of tracheary elements. When all evidence is considered, it becomes apparent that Pelecyphora aselliformis and Encephalocarpus strobiliformis are cogeneric as are P. valdeziana and P. pseudopectinata. Yet, the two cogeneric pairs are not closely related to each other. We do not propose to place them in any phylogenetic scheme as yet because general knowledge of the family Cactaceae is still too fragmentary. The first pair is assigned to Pelecyphora, of which a formal taxonomic treatment is presented, and the second pair is tentatively assigned to Thelocaclus.
RNA AND PROTEIN METABOLISM IN SENESCENT SHOOT APICES OF ‘ALASKA’ PEAS
Authors: Ecklund Paul R. , Moore Thomas C.
Published: January 2018

Senescence of shoot apices of Pisum sativum L. ‘Alaska’ as measured by cessation of stem elongation was delayed by removal of flowers. Analyses of total RNA, nitrogen, protein and inorganic phosphorus in shoot tips of deflowered and control (flower‐ and fruit‐bearing) plants throughout ontogeny revealed that the levels of all these metabolites declined during senescence. Also throughout ontogeny shoot tips of control and deflowered plants were compared with respect to their ability to enzymically degrade RNA and to take up and incorporate P32‐orthophosphate into RNA. The specific activity of ribonuclease increased as senescence progressed while the absolute activity appeared to decrease in correlation with a decrease in total nitrogen content. Compared with nonsenescing shoot tips, senescing shoot tips accumulated less P32 but exhibited an apparent enhancement of P32 incorporation into RNA, which was attributed to a reduction in the endogenous phosphorus pool causing a smaller dilution of the accumulated P32. It is concluded that decreases in the levels of RNA, protein and inorganic phosphorus and in the tran‐spirational uptake of nutrients are factors correlated with senescence of the shoot apex.
MORPHOLOGY OF CHAETOMIUM ERRATICUM
Authors: Cooke John C.
Published: January 2018

Development of perithecia from single, uninucleate ascospores disclosed a homothallic condition for Chaetomium erraticum. This species was found to produce sessile ascogonial coil initials from uninucleate vegetative cells that become enveloped by hyphae formed at the base of the ascogonium. The ascogonium consists of several cells that are uninucleate or binucleate. A perithecium forms from numerous divisions and enlargement of the surrounding uninucleate cells. Differentiation of the perithecial cells results in the formation of a carbonaceous wall, perithecial hairs, and an ostiole lined with periphyses. A convex hymenial cluster of ascogenous cells forms in the lower half of the centrum from which typical croziers develop. Asci push up into the pseudoparenchyma cells of the centrum. The growth of the ascogenous system is in part responsible for increase in perithecial size. The breakdown of the pseudoparenchyma cells around the developing asci results in the formation of a central cavity in which ascospores are released when the asci deliquesce. No paraphyses are present. The type of development and features of the centrum of C. erraticum and other species of Chaetomium indicate a distinct Xylaria‐type centrum.
TEMPERATURE‐SENSITIVE MUTANTS OF ASCOBOLUS IMMERSUS
Authors: Yu‐Sun Clare C. C.
Published: January 2018

As a result of a search for genetic markers to be used in interallelic recombination studies, 23 temperature‐sensitive mutants of Ascobolus immersus were isolated following UV‐irradiation. Three of these failed to grow at 37 C but grew normally or, in one case with a colonial phenotype, at 25 C. Twenty mutants are like the wild type at 25 C but express a colonial phenotype at 37 C. Crosses of the mutants to wild type indicate that all are due to single‐gene mutations. Crosses among certain of the mutants indicate that several different loci are affected.
CHROMOPLASTS OF TOMATO FRUITS. II. THE RED TOMATO
Authors: Harris William M. , Spurr Arthur R.
Published: January 2018

Plastid transformation at the ultrastructural level in a normal red tomato ‘Pearson’ is reported. During ripening, lycopene aggregates on thylakoid membranes. These thylakoids lengthen and sometimes are associated in concentrically layered groups forming very elongated or irregular crystalloids. Thylakoid plexes often occur. Comparisons of the mature chromoplasts of the normal red tomato with those of other pigment lines indicate that differences in carotenoids markedly affect ultrastructure.
AUXIN DESTRUCTION BY MARASMIUS PERNICIOSUS
Authors: Krupasagar V. , Sequeira L.
Published: January 2018

Attempts were made to determine whether Marasmius perniciosus Stahel., causal agent of the witches' broom disease of cacao, produces substances that could elicit on the host some of the symptoms which are characteristic of the disease. In vitro the fungos did not produce significant amounts of cytokinins or auxins. However, culture filtrates destroyed indole‐3‐acetic acid (IAA) rapidly because of two different IAA‐oxidizing enzymes: (1) a peroxidase (IAA oxidase) characterized by (a) dependence on Mn++ and 2,4‐dichlorophenol (DCP), (b) pH. optimum of 3.0, (c) inactivation at 85 C for 5 min, (d) stimulation of oxidative activity by addition of 0.3 μmole/ml H2O2; and (2) a laccase characterized by (a) no dependence on Mn++ and DCP, (b) pH optimum of 6.0, (c) inactivation at 95 C for 5 min, (d) ability to oxidize IAA and phenolic substrates in the absence of H2O2. The peroxidase was completely inhibited by scopoletin (0.0002 m) ; the laccase was inhibited by thiourea (0.1 m). The laccase could be separated from the peroxidase by elution through a column of Sephadex G‐100. It is suggested that the main pathogenic effect of the fungus may be associated with these auxin‐inactivating systems.
AN ELECTRON MICROSCOPE STUDY OF GERMINATING LYCHNIS ALBA POLLEN
Authors: Crang Richard E. , Miles G. Bruce
Published: January 2018

The fine structure of germinating Lychnis alba pollen is described and correlated with some basic tests for chemical composition. The primary storage product in both pollen grain and pollen tube appears to be lipid. Pregermination synthesis of pollen tube wall material appears characteristic in this species, along with the presence of crystalloid structures having approximately 80 A periods. The crystalloid bodies are not found in the tip cytoplasm of the pollen tubes. Limited acid phosphatase activity is found associated with the crystalloid structures as well as within vesiculate structures of the pollen grain. The cytoplasmic structure of both the pollen grains and pollen tubes is characterized by few dictyosomes and plastids and no microtubules, although mitochondria and polyribosomes are abundant. Pectins have not been verified in the pollen tube walls, their primary composition being cellulose.
FINE STRUCTURE OF PETROBINAE (COMPOSITAE‐HELIANTHEAE) POLLEN WALLS
Authors: Skvarla John J. , Turner B. L.
Published: January 2018

Pollen of the subtribe Petrobinae (Compositae‐Heliantheae) was examined by light and electron microscopy. Surface morphology and fine structure of all species examined were identical; these characters also were similar to pollen of other Heliantheae subtribes examined in previous studies.
THE FERTILE SPIKE OF OPHIOGLOSSUM PETIOLATUM. I. MECHANISM OF ELONGATION
Authors: Peterson R. L. , Cutter Elizabeth G.
Published: January 2018

The frond of Ophioglossum consists of a sterile segment and a fertile segment or spike. An investigation of fertile spike elongation reveals that growth of the spike proceeds by activity of an intercalary meristem located in the most distal region of the peduncle subtending the sporangial area. Anatomical comparisons of all regions of developing spikes, counts of mitotic figures along the length of spikes of various ages, determination of cell lengths of peduncle ground parenchyma cells, and historadioautography of spikes treated with H3‐thymidine confirms the presence in the apical portion of the peduncle of a region of frequently dividing cells intercalated between two regions of more mature tissues. Marking experiments indicate that the petiole of the sterile segment of the frond elongates in a similar fashion. Although this type of intercalary meristem is rather common in angiosperm flower scapes and peduncles, this is the first detailed analysis of this type of growth in a pteridophyte genus.
MICROSPECTROPHOTOMETRIC INVESTIGATIONS OF FREE SPACE IN PLANT CELL WALLS
Authors: Berlyn Graeme P.
Published: January 2018

Two equations were proposed for the determination of free space in plant cell walls. Solution of the equations required microspectrophotometric measurements of cell walls after introduction of a chromophore. A periodic acid‐Schiff test was developed for this purpose and a statistical analysis of the error terms was used to evaluate the discriminatory capacity of the system. Bouguer's law was tested directly and found to hold for the tissue thicknesses and wavelengths used. Because concentration was unknown, Beer's law could not be tested directly, but a new method based on the logarithmic transformation of the optical densities and statistical correlation of curve shape was used to predict the wavelength interval in which Beer's law held. Calculations by a newly derived extinction‐ratio equation (AE/E) were essentially invariant over the predicted range and variable outside of this wavelength interval. Free space in hydrated S2 layers of tracheid cell walls of Pinus resinosa Ait. was calculated to be about 25%. The magnitude of free space at various stages of hydration was also tabulated. Considerable free space was found to exist in plant cell walls after prolonged exposure to anhydrous ethyl alcohol; however, after complete dehydration there was little evidence of residual free space.
A CONTRIBUTION TO THE EARLY TERTIARY FOSSIL RECORD OF THE SALVINIACEAE
Authors: Jain Raj K. , Hall John W.
Published: January 2018

Megaspores and massulae of Azolla, Azollopsis, and Salvinia are recorded from the Paleocene and Eocene of Montana and the Dakotas. Three new species of Azolla are described and two species of Azolla are redescribed. The columella of the floating apparatus of the megaspore apparatuses of Azolla appears to be a phylogenetic localization of the perispore around the megaspore. A new section of Azolla (section Kremastospora) is created for species whose megaspore apparatuses have many floats and whose massulae have hooked (anchor‐shaped) glochidia. Salvinia preauriculata is based only on leaf remains from the Eocene of North America. Megaspores and massulae which probably are conspecific with the leaf remains are described. The megaspores and massulae of the fossil species are much smaller than those of the living species, S. auriculata, with which S. preauriculata has been compared. The similar size of the megaspores and massulae of the fossil species suggests a less specialized condition than in living species, where these two structures differ greatly in size. Azollopsis tomentosa, previously known from the late Cretaceous, has been found in the Eocene.
RESPONSE TO CARBON MONOXIDE BY GEOGRAPHIC VARIANTS IN ACACIA FARNESIANA
Authors: McMillan Calvin , Cope Jess M.
Published: January 2018

Differences in degree of defoliation in CO‐air mixtures were shown by geographic variants in Acacia farnesiana (L.) Willd., a widespread, weedy, pantropic, leguminous tree. Laboratory‐germinated seedlings from Mazatlán (MAME‐1), Sinaloa, Mexico, showed greater sensitivity to a CO gradient than plants from Point Tuna (PORO), Puerto Rico. Seedlings of both strains grown under a light intensity of 200 ft‐c showed greater sensitivity to CO than those grown under 1,800 ft‐c. When intact plants of 17 geographic variants grown at low‐light intensities were exposed to 2% CO in air, 11 strains (Mexico, 8; Texas, 1; California, 1; Guatemala, 1) showed almost complete defoliation. The other six strains—from Brazil, Hawaii, Puerto Rico, Italy, Algeria, and Micho‐acán, Mexico—showed defoliation averaging from 23 to 70%. The significance of the CO‐de‐foliation response is difficult to explain in terms of the natural distribution of A. farnesiana. It is suggested that this response may be correlated with some biochemical process of adaptive significance.
THE EFFECTS OF AUXIN, ACTINOMYCIN D, ETHIONINE, AND PUROMYCIN ON POST‐POLLINATION BEHAVIOR BY CYMBIDIUM (ORCHIDACEAE) FLOWERS
Authors: Arditti Joseph , Knauft Robert L.
Published: January 2018

Application of NAA to Cymbidium stigmas induces anthocyanin formation in columns and labella as well as swelling of the former, stigmatic closure, and wilting of sepals and petals. All of these are aspects of post‐pollination behavior by orchid flowers. Anthocyanin formation and wilting, but not swelling of the column and stigmatic closure, can be inhibited by actinomycin D, ethionine and puromycin. This suggests that anthocyanin formation and wilting require de novo DNA‐dependent RNA synthesis and production of new proteins. Swelling of the column and stigmatic closure, on the other hand, are apparently independent of such new synthesis and may be brought about by the activation of pre‐existing compounds.
THE QUANTIFICATION OF SOME PLANT‐TAXA CIRCUMSCRIPTIONS
Authors: Gilmartin Amy Jean
Published: January 2018

Intrataxon variability is estimated by the technique of numerical taxonomy. Taxa which had been determined by orthodox taxonomic methods are subjected to analyses by numerical phenetics. Comparisons are made of the amounts of cohesion among the members of different taxa in the Bromeliaceae at several taxonomic levels by computing the degrees of similarities between members of the same taxon and of different taxa. Results of these comparisons with several taxa reveal that the variability of a taxon in terms of phenetic distance computed with a large number of characters does not necessarily agree with a subjective appraisal of variability. The method facilitated difficult taxonomic determinations and provided an estimate of the relative evolutionary ages of different taxonomic groups.
THE CONTROL OF ALLELIC RECOMBINATION AT HISTIDINE LOCI IN NEUROSPORA CRASSA
Authors: Catcheside D. G. , Austin Barbara
Published: January 2018

The gene rec‐1+ which reduces allelic recombination at the his‐1 locus by a factor of between 15 and 30 has no effect upon allelic recombination at the his‐2, his‐3, his‐5, his‐6 and his‐7 loci. Other genes controlling recombination at two of these loci, namely rec‐x at his‐2 and rec‐w at his‐3, have been found. There is a strong possibility that rec‐x may be identical with rec‐3, so far known to regulate recombination only at the am‐1 locus. It is probable that the stocks used all carry a rec+ gene which regulates recombination at the his‐6 locus, since all prototroph frequencies are low, but no regulatory gene active at the his‐5 and his‐7 loci.
COMPARATIVE STUDIES ON THE BEHAVIOR OF ALLOGAMOUS PENNATE DIATOMS IN AUXOSPORE FORMATION
Authors: Geitler Lothar
Published: January 2018

Auxospore formation by allogamy in pennate diatoms has been known for a long time, but more recently many kinds of peculiar behavior have come to light. An example of these is the amazing and quite unexpected relationships existing between the alternative site of epi‐ and hypotheca and the establishment of plasmatic gradients in the cell on the one hand and the determination of mating types on the other. Furthermore, there are remarkable specific relations between the formation of copulation‐tubes (or canals) and the mode of pairing, as well as the kind of gamete fusion. There are, too, specific relationships between the mode of gamete fusion and the position of the polar axes in the auxospores and the primary cells. Although there are great variations, one can determine certain types and rules of behavior in pairing and auxospore formation. On the other hand there are certain events, e.g., a “spontaneous plasmolysis” in the auxospores of some races of Navicula cryptocephala, by which the abnormal shape of the primary cell—otherwise inevitable—is avoided.
EFFECT OF BLUE AND YELLOW LIGHT DURING THE LATER DEVELOPMENTAL STAGES OF SPHAEROBOLUS
Authors: Ingold C. Terence
Published: January 2018

When fruiting cultures of Sphaerobolus are transferred from continuous light to darkness the discharge of global masses continues for 1 day but then stops for the next few days. Experiments are reported in which this darkness is interrupted after 24 hr by brief (0.5‐2 hr) treatment with light of different wavelengths and of equated low intensity (ca. 100 lux). Interruption by blue (ca. 448 mμ) or by green (ca. 500 mμ) light has no effect, but treatment with yellow (ca. 585 mμ) or red (ca. 650‐700 mμ) leads to substantial discharge 24 hr later. If, however, the yellow treatment is followed immediately with blue there is little or no discharge; but if the order of this treatment is reversed, a high level of discharge results. This is somewhat greater than that resulting from treatment with yellow light alone. If, following a yellow treatment there is an interval of several hours before a blue treatment, the blue has less effect in negating the action of the yellow light. It is shown that, although in the final light‐sensitive stages in development of the sporophore before it opens, yellow and red light are stimulatory but blue and green are not; in the phototropic response of the mature sporophores blue light is effective and yellow is not.
COMBINED EFFECT OF 6‐BENZYLAMINOPURINE, GIBBERELLIC ACID, AND 3‐INDOLEACETIC ACID ON THE EXPANSION OF ISOLATED PUMPKIN COTYLEDONS
Authors: Kursanov A. L. , Kulaeva O. N. , Mikulovich T. P.
Published: January 2018

The effect of 6‐benzylaminopurine, gibberellin, and 3‐indoleacetic acid, used separately or in combinations, on the expansion of isolated pumpkin cotyledons has been studied. All three types of phytohormones can promote the expansion of isolated cotyledons. The resulting effect depends on the concentration of the particular phytohormone and on its quantitative ratio with the other phytohormones. The optimum combinations of phytohormones introduced externally varied according to the seed. The stimulating effect on the expansion of cotyledons is evidently exerted by those phytohormones which are present in the seeds in minimum amounts. An analysis of the concentration curves of the phytohormone effect indicates that they are not interchangeable as regards their influence on the expansion of isolated pumpkin cotyledons.
ON THE METHODS OF EXPERIMENTAL TAXONOMY
Authors: Müntzing Arne
Published: January 2018

By studying seedling progenies from individual plants it may be decided whether the material under investigation is allogamous, autogamous or apomictic. Chromosome counts disclose whether the material is cytologically stable or variable. If variation occurs it may be a question of polyploidy or aneuploidy. Aneuploidy may either be an occasional consequence of polyploidy or it may represent dysploidy and the formation of new basic numbers. Chromosome counts combined with measurements of chromosome size may reveal cases of pseudopolyploidy of the kind first observed in Luzula. If chromosome morphology is different between two taxa this indicates reproductive isolation. Different species usually differ with regard to their chromosome structure. Studies of meiosis are desirable in polyploids in order to distinguish between auto‐ and alloploidy. Cases of genic control of meiosis in polyploids of Phleum and Triticum demonstrate, however, that partial or complete homology between genomes does not always result in multivalent formation. Apparent alloploids may in reality be more or less autoploid. Incompatibility is not a reliable criterion of species differentiation. Strong or absolute barriers between diploids and autotetraploids may have purely quantitative causes. Hybrid sterility is not always a reliable measure of the degree of genetic difference between the parents, but may be caused by heterozygosity for chromosomal rearrangements. Cytological and experimental methods are, nevertheless, indispensable tools in plant taxonomy.
ULTRASTRUCTURE OF ONION ROOTS INFECTED WITH PYRENOCHAETA TERRESTRIS, A FUNGUS PARASITE
Authors: Hess W. M.
Published: January 2018

Onion roots of varieties ‘951’ and ‘Excel’ were infected under artificial conditions by a virulent isolate of the onion pink‐root fungus, Pyrenochaeta terrestris. Roots of variety ‘951’ were penetrated initially at the tip while roots of variety ‘Excel’ were penetrated initially 2 cm or more back from the tip. Ultrastructural observations of infected roots of both varieties indicated that the fungus penetrated primarily or entirely by dissolution of host cell walls, rather than by pressure of fungal cells. In both varieties the fungus caused cell disruption one to several cells in advance of the fungus. In addition, the same isolate of the pink‐root fungus was grown on paper consisting primarily of gymnosperm cells. The remnants of cell walls were dissolved by the fungus with no evidence of physical pressure by the fungus.
STENOKOLEOS BIFIDUS SP. N. IN THE UPPER DEVONIAN OF NEW YORK STATE
Authors: Matten L. C. , Banks H. P.
Published: January 2018

Stenokoleos is a genus for petrified axes from the Mississippian New Albany Shale to which an Upper Devonian occurrence in New York is added. Two orders of branching were known and the plant was thought to be related to coenopterid ferns. The new petrified axes from New York reveal three orders of branching. A pair of rachides emerges from one side of the stem at each node. Their position alternates at successive nodes (distichous). Each rachis bears alternately arranged pinnae. The shape of the xylem strand and the number of protoxylem areas are variable. Traces to the pairs of rachides arise either as two separate strands or as a single strand that is presumed to divide while still within the cortex of the stem. Traces to pinnae are ellipsoid or clepsydroid. Tracheids are scalariform and uni‐ or biseriate, circular‐bordered pitted. Peripheral loops are present in all orders of branches. Protoxylem strands are numerous and maturation is mesarch. Cortex is parenchymatous where it is preserved but outer cortex is missing. Stenokoleos and Reimanniopsis are placed in a new family, Stenokoleaceae. This is classified as Incertae Sedis among Pterophytina in Tracheophyta. It is suggested that the plant is related more closely to the Mississippian pteridosperms Tristichia and Tetrastichia than to the coenopterid ferns.
MORPHOLOGY AND LIFE CYCLE OF A NEW CHYTRID WITH AERIAL SPORANGIA
Authors: Voos Jane Rhein
Published: January 2018

An investigation of the life cycle of Caulochytrium gloeosporii Voos and Olive, a parasite of Gloeosporium, has confirmed the existence of an alternation of generations. Zoospores from sessile sporangia may develop vegetatively into similar sporangia or they may function as isogametes, fusing in pairs to produce cysts (zygotes) that give rise to slender‐stalked aerial sporangia. Meiosis is believed to occur in the aerial sporangium, which at germination liberates eight asexual zoospores. The species is homothallic.
MORPHOLOGY AND DEVELOPMENT OF THE FLOWERS OF BOOTTIA CORDATA, OTTELIA ALISMOIDES, AND THEIR SYNTHETIC HYBRID (HYDROCHARITACEAE)
Authors: Kaul Robert B.
Published: January 2018

The inferior ovary of Boottia cordata, Ottelia alismoides, and their hybrid is appendicular in nature, the carpels are congenitally only slightly connate, and they are unsealed. All floral organs except the sepals originate from common primordia in the female and bisexual flowers. A flat residual floral apex is pressnt. There is a vestigial superior ovary of three ontogenetically fused carpels in the male flower of Boottia cordata. The hybrid is intermediate in many characteristics and has partially fertile stamens and staminodia. The sequence of development in all flowers is acropetal. These plants appear to be related to the Butomaceae and they show evolutionary tendencies parallel to those in the Nymphaeaceae.
CHLOROPHYLL CATALYSIS AND EINSTEIN'S LAW OF PHOTOCHEMICAL EQUIVALENCE IN PHOTOSYNTHESIS
Authors: Warburg Otto , Krippahl Günter , Lehman Arnold
Published: January 2018

We describe the catalysis of photosynthesis by chlorophyll: (a) chlorophyll bound to carbonic acid (that is, the photolyte) absorbs 1 quantum of light and is thereupon split into oxygen, reduced carbonic acid, and free chlorophyll; (b) the photolyte (that is, chlorophyll bound to carbonic acid) is resynthesized from carbonic acid and free chlorophyll with the help of the energy derived from the reoxidation of two‐thirds of the reduced carbon formed in the light reaction. For calculation of the true quantum requirement of photosynthesis from experimental measurements, it is necessary to measure the light absorbed by the photolyte only, since the light energy absorbed by free chlorophyll is not used in the oxygen development of photosynthesis. To eliminate the loss of the light absorbed by the free chlorophyll, the factor ɛ = photolyte/total chlorophyll must be introduced into the calculation. Failure to take ɛ into consideration has led to discrepancies of 1,000% between the quantum yields obtained in different laboratories. These discrepancies are now removed. The quantum requirement of the splitting of the photolyte is always 1.
MONOGRAPH OF THE GENUS PROTOSTELIUM
Authors: Olive Lindsay S. , Stoianovitch Carmen
Published: January 2018

Three new species of Protostelium (Order Protostelida of the Mycetozoa) are described: P. irregularis, P. zonatura, and P. pyriformis, all with rather wide distribution and occurring on dead attached plant parts, less often in soil and humus. The latter two species differ from the first and from the other two known species, P. mycophaga Olive and Stoianovitch and P. arachisporum Olive, in the endogenous origin of the stalk. P. mycophaga var. crassipes, with vesicular stalk bases, is the third variety of that species to be described. A key to the genus is included.
LIGHT MICROSCOPE INVESTIGATION OF SIEVE‐ELEMENT ONTOGENY AND STRUCTURE IN ULMUS AMERICANA
Authors: Evert Ray F. , Tucker C. Milton , Davis Jerry D. , Deshpande Bharati P.
Published: January 2018

At maturity the sieve elements of Ulmus americana L. contain a parietal network of very fine strands of slime which is continuous from one sieve element to the next through the sieve‐plate pores. Upon injury this parietal network, which is derived from the slime bodies of immature sieve elements, sometimes becomes distorted into longitudinally oriented strands. Some of these strands frequently extend the length of the cells and often are continuous from one sieve element to the next through the sieve‐plate pores. At times past such strands have erroneously been interpreted as normal constituents of the mature sieve‐element protoplast. Many mature sieve elements of U. americana contain nuclei, which apparently persist for the life of the sieve elements. In addition, some evidence has been found in mature sieve elements for the presence of a membrane which delimits the parietal layer of cytoplasm, including its network of slime strands, from the vacuolar region of the cell.
COMPOUNDS FROM THE STIGMAS OF TEN SPECIES
Authors: Martin Franklin W.
Published: January 2018

Extracts of the intact stigmatic surface of 10 species from different families contained little or no free sugar. The principal components of the extracts consisted of phenolic (anthocyanins, flavonoids, cinnamic acids) and lipid compounds. The phenolic compounds occurred as glycosides or esters. Phenolic compounds could inhibit insects and diseases, stimulate or inhibit pollen germination, or provide specificity to the pollen selection‐germination process of the stigma by interacting with growth‐regulators or related compounds.
STUDIES ON FOSSIL AZOLLA: PRIMITIVE TYPES OF MEGASPORES AND MASSULAE FROM THE CRETACEOUS
Authors: Hall John W.
Published: January 2018

Fossil Salviniaceae are described from the Claggett Shale and Judith River Formation, late Cretaceous (Campanian stage) of Montana. A new genus, Parazolla, from the Claggett Shale, has megaspores in which the swimming apparatus is composed of a number of elongate floats attached to the megaspore body and invested by coiled hairs. The floats separate at maturity. Massulae (bearing microspores) have simple hair‐like glochidia, many of which are knobbed at their tips. Glochidia tend to resemble the perisporial hairs of the megaspore body. This resemblance provides fossil evidence of the homology of these two hair‐like structures among living species of Azolla. In Azolla simplex from the Judith River Formation the megaspore has a single cap‐like so‐called columellate float. Massulae, which have anchor‐shaped glochidia, are associated with these megaspores. A. simplex is the oldest species of Azolla and Parazolla the oldest member of the Salviniaceae so far found.
ASSORTATIVE POLLINATION IN LYTHRUM
Authors: Levin Donald A.
Published: January 2018

The pollination patterns of bees and butterflies were observed in an assemblage composed of 57 plants of Lythrum alatum and 30 plants of L. salicaria. Lythrum salicaria was preferred by both groups of pollinators as indicated by the greater number of flights from this species as compared to flights from L. alatum. The degree of assortative pollination was measured in both groups of pollinators and was greater in bees. Fidelity in bees appeared to be in response to species attractiveness, whereas in butterflies it appeared to be in response to species balance.
THE KINETICS OF INITIAL NUCLEAR EXCHANGE IN COMPATIBLE AND NONCOMPATIBLE MATINGS OF SCHIZOPHYLLUM COMMUNE
Authors: Leary John V. , Ellingboe Albert H.
Published: January 2018

The effect of mating‐type factors on exchange of nuclei between mycelial fragments mated in liquid culture was studied. Evidence for exchange of nuclei was based on three criteria for detecting nuclei from both mating partners in mycelial fragments of the developing dikaryon or hetero‐karyon. The kinetics of nuclear exchange were shown to be relatively independent of the method used. It was shown that the kinetics of nuclear exchange in the first 96 hr are different in the compatible (A41 B41 × A42 B42), common‐A (A42 B42 × A42 B41), common‐B (A41 B42 × A42 B42), and common‐AB (A41 B41 × A41 B41) matings. In all four types of matings, the percentage of fragments possessing both types of nuclei 12‐24 hr after mating is nearly equal. After this time, significant differences appear in the patterns for compatible vs. the three non‐compatible matings and the common‐A vs. the common‐B and common‐AB matings. The percentage of mycelial fragments possessing both types of nuclei throughout the 96‐hr test period is similar for both the common‐B and common‐AB matings. The kinetics of nuclear exchange were shown to be independent of the particular mating‐type alleles and nutritional markers used. When the efficiency of nuclear exchange in complete and minimal media was compared, it was shown that nuclear exchange occurred more rapidly and synchronously in minimal medium. This difference is not due to growth differences in the two media. These data indicate that the earliest mating interactions, i.e., hyphal anastomosis and nuclear exchange, are independent of the mating‐type factors but that subsequent events are determined by these genes.
RELATION OF PLASTOCHRON TO ANATOMY AND GROWTH IN THE SHOOT APEX OF CHRYSANTHEMUM
Authors: Berg Arthur R.
Published: January 2018

The relation between plastochron stage, apical anatomy, and thymidine‐C14 incorporation was studied in the shoot apex of Chrysanthemum morifolium ‘Albatross.’ Apices were sorted into early, middle, and late plastochron stage under a dissecting microscope, fixed, and sectioned longitudinally so that median sections included known sectors of the apical flank. Study of these sections revealed no discernible difference between apices in early, middle, or late plastochron with respect to regularity of cell pattern, presence of a cambium‐like zone, appearance of the second tunica layer or staining pattern with pyronin or with toluidine blue. Likewise, apices that had been treated with thymidine‐C14 for 2‐4 hr showed no differences between the three stages in number or distribution of labeled cells.
IDANOTHEKION GEN. N., A SYNANGIATE POLLEN ORGAN WITH SACCATE POLLEN FROM THE MIDDLE PENNSYLVANIAN OF ILLINOIS
Authors: Millay Michael A. , Eggert Donald A.
Published: January 2018

Idanothekion glandulosum gen. et sp. n. is a synangiate pollen organ represented by approximately 30 specimens contained in coal balls from the middle Pennsylvanian of Illinois. Each synangium is composed of seven to nine elongate sporangia that are fused laterally for approximately four‐fifths of their length, and are radially arranged about, and fused to, a short central column; the central column is restricted to the proximal one‐third of the synangium. Distal to the column the sporangia surround a hollow central area. Dehiscence occurred by means of a longitudinal slit along the mid‐line of the inner face of each sporangium. The outer walls of the sporangia have a complex histology involving an external epidermis, a middle presumably glandular layer containing scattered enlarged cells, and an inner layer made up of thin‐walled parenchyma. Vascular tissue is present in the central column and outer walls of the sporangia. Each sporangium has a prominent, attenuate, multicellular tip. Large numbers of saccate pollen grains similar to those found in numerous fossil and extant coniferophytes as well as some Mesozoic pter‐idosperms were produced in each sporangium. Idanolhekion resembles some synangia assignable to Paleozoic members of the Marattiales; however, the new genus compares most closely with pollen organs believed to have been produced by members of the Pteridospermales. It seems most likely that Idanothekion represents the pollen organ of some member of the Lyginopteridaceae that produced pollen of a type which up to now has not been known from Paleozoic seed ferns.