bluuebunny/crossref_metadata_2025 huggingface dataset:
THE PROBLEM OF PLOIDY IN ECHEVERIA (CRASSULACEAE) I. DIPLOIDY IN E. CILIATA
Authors: Uhl Charles H.
Published: January 2018

The largely Mexican genus Echeveria is characterized by an extensive series of dysploid chromosome numbers, with every gametic number from 12 to 34 known in at least one species. Within this nearly three‐fold range of numbers, the boundary between diploidy and tetraploidy is not immediately apparent. However, species of Echeveria can be hybridized in an extraordinary number of combinations, both among themselves and with related genera, and study of the morphology of the hybrids and the pairing of their chromosomes provides information that helps to identify the ploidy of the parents. This paper reports observations from study of 80 hybrids between E. ciliata (n = 25) and 73 other species and/or cytotypes. Hybrids between E. ciliata and definite diploids are all nicely intermediate morphologically, whatever the chromosome numbers. In these same hybrids, most chromosomes become involved in pairing at meiosis, and the number of paired elements (bivalents and multivalents) approaches or equals, but never exceeds, the number of chromosomes received from the lower‐numbered parent. In most cells, relatively few univalents are present, sometimes none. These observations are considered to indicate that all paired elements include at least one chromosome from each parent and therefore that pairing occurs between chromosomes of different parents only (allosyndesis). Since none of the 25 gametic chromosomes of E. ciliata is able to pair with any other, although they do pair very extensively with chromosomes from many other species having a wide range of numbers, E. ciliata is considered to be diploid in spite of its relatively high chromosome number. On the other hand, hybrids of E. ciliata with definite polyploids resemble the latter much more closely in their morphology, and at meiosis most or all pairing occurs by autosyndesis between chromosomes received from the polyploid parent, while the chromosomes from E. ciliata generally remain unpaired. In these respects most, but not all, species of Echeveria having as many as 34 gametic chromosomes have the same properties as E. ciliata and also are considered to be diploid. The ancestral chromosome number in the genus is not clear, but it is probably near the upper end of the series of dysploid numbers.
CULTURE OF MATURE ECOTYLEDONOUS EMBRYOS OF PHASEOLUS VULGARIS AND THE NUTRITIONAL ROLE OF COTYLEDONS
Authors: Monnier Michel
Published: January 2018

Embryos of Phaseolus vulgaris L. were excised from seeds and cultured with cotyledons removed to determine the actions of various cultural conditions upon embryo development. Four media were tested, but ecotyledonized embryos did not grow as rapidly on any of them as did embryos with intact cotyledons on agar‐water media. Comparisons of growth of ecotyledonized embryos with embryos bearing fractions of cotyledons indicated ecotyledonized embryos cultured on nutrient media grew about as well as embryos bearing cotyledons from which 97% of the volume had been removed surgically. The final weight of ecotyledonized embryos was greater when detached cotyledons were placed near them and was even greater when extracts of detached and incubated cotyledons were employed in the nutrient medium. Benzyladenine, kinetin, gibberellic acid, indole‐acetic acid, presence of sucrose, and light or dark culture failed to enhance the ability of incubated cotyledons to stimulate growth of embryos.
EVOLUTION OF LEAF ARCHITECTURE IN THE CHAPARRAL SPECIES FREMONTODENDRON CALIFORNICUM SSP. CALIFORNICUM (STERCULIACEAE)
Authors: Bissing Donald R.
Published: January 2018

The chaparral species Fremontodendron californicum ssp. californicum and the cloud forest species Cheirostemon platanoides arose from a common mesophytic stock. The leaf of C. platanoides is proposed as a model for the ancestral leaf and provides an architectural baseline allowing identification of the types and relative magnitudes of morphological and anatomical modifications which have occurred in the leaf of F. californicum. The leaf of F. californicum reflects intense selection for reduced surface area; however, both deletion and addition of lobes has occurred. Vein density has increased due to a greater number of more highly branched terminal veinlets. Mechanical structures, i.e., sclerenchyma, cuticle, show a quantitative reduction; whereas, water storage tissue, i.e., mucilage cells, has been augmented at the expense of spongy mesophyll. The leaf has become weakly isolateral and the number of palisade strata has increased. No increase in the volume of palisade tissue per unit volume of mesophyll is apparent due to a reduction in palisade cell length and palisade packing density. Total leaf thickness has not increased. The indumentum shows selection for non‐living, pedestalled stellate trichomes which form a transpiration‐limiting canopy above the stomata. Stomatal density has decreased while guard cell dimensions have become larger. Some structural modifications in F. californicum appear to have evolved directly in response to long‐term water stress, others seem more directly related to leaf diminution. Xeroplastic changes in foliar structure are in some cases unreliable indicators of ultimate xeromorphic modifications arising in an evolutionary context.
GERMINATION ECOPHYSIOLOGY OF ARENARIA GLABRA, A WINTER ANNUAL OF SANDSTONE AND GRANITE OUTCROPS OF SOUTHEASTERN UNITED STATES
Authors: Baskin Jerry M. , Baskin Carol C.
Published: January 2018

The germination ecophysiology of Arenaria glabra Michx., a characteristic winter annual plant species of granite and sandstone outcrops of southeastern United States, was investigated. Seeds germinate in early autumn, plants overwinter in the rosette stage and then flower, set seeds, and die in late spring; seeds are dispersed soon after maturity. Eighty‐five to 90% of freshly‐matured seeds were innately dormant, and the other 10–15% germinated only at temperatures lower than those that occur in the habitat at the time of seed dispersal in June. During the summer after‐ripening period, seeds stored dry under ambient laboratory conditions exhibited progressive increases in rates and total percentages of germination, a widening of the temperature range for germination, and a loss of the light requirement. At a 14‐hr daily photoperiod, seeds kept on continuously moist soil germinated to 83% at simulated July and August temperatures during July and August, and the remainder germinated at September temperatures in September. On the other hand, seeds subjected to alternate wetting and drying during July and August germinated to only 9% during those 2 months, and the remainder germinated after the soil was kept continuously moist, beginning on 1 September, at simulated habitat temperatures during September and October. Thus, the timing of germination of A. glabra in the field is controlled by an interplay of the seeds' physiological state with the dynamics of temperature and soil moisture conditions.
VENTILATION BY FLOATING LEAVES IN NUPHAR
Authors: Dacey J. W. H. , Klug M. J.
Published: January 2018

The network of internal gas spaces in the yellow waterlily constitutes a pressurized flow‐through system which forces oxygen to the rhizome buried in anaerobic sediment. This ventilation has been documented previously in a subspecies of Nuphar luteum with aerial leaves, and appeared to occur only during daylight when the leaves are warmed by the sun's radiation. In this study we have found the ventilation system operating in two different subspecies of N. luteum growing in Alaska and in Massachusetts. These plants have floating leaves so that during certain times of the year the leaves are warmed not only by the sun in daylight but also by lake water at night, allowing the ventilation to continue during darkness.
OBSERVATIONS ON STELAR PARENCHYMA IN LEPIDIUM SATIVUM L. ROOTS
Authors: Peterson R. L.
Published: January 2018

Seedlings of Lepidium sativum L. (cress) were germinated and grown under ten different growth conditions to assess the effects of environment on root stelar parenchyma development. Stelar parenchyma did not undergo autolysis in any of the treatments, refuting an earlier suggestion that certain ‘prostelar’ cells (cells adjacent to primary xylem and primary phloem) are replaced by cambial derivatives.
ULTRASTRUCTURE OF SPOROGENESIS IN THE MOSS, AMBLYSTEGIUM RIPARIUM I. MEIOSIS AND CYTOKINESIS
Authors: Brown Roy Curtiss , Lemmon Betty E.
Published: January 2018

Emphasis is placed on three aspects of meiosis in the moss Amblystegium riparium (Hedw.) BSG: 1***) nature of the sporogenous layer; 2) prophasic microtubules and polarity; and 3) cleavage pattern. Spore tetrads develop while still encased by archesporial cell walls. The cellular nature of the sporogenous layer differs from the more usual occurrence of free sporocytes released into a common spore sac. Two important events mark the establishment of sporocyte polarity during meiotic prophase: 1) migration of the four plastids to the distal tetrad poles (telophase II poles); and 2) ingrowth of the sporocyte wall in eventual cleavage planes between the tetrad poles. An extensive, plastid‐based microtubule system is associated with organelle migration during the establishment of sporocyte polarity in meiotic prophase. Disruption of the nuclear envelope in prometaphase I occurs at sites opposite the four plastids where microtubules extend from plastid envelope to nuclear envelope. Formation of a cell plate following the first meiotic division results in a dyad, whereas in many mosses meiosis is completed in the undivided sporocyte and is followed by simultaneous cleavage into a spore tetrad. Spore cleavage is accomplished by vesicular coalescence resulting in septa that coincide with the prophasic wall ingrowths.
CHANGE IN EPILOBIUM PHYLLOTAXY DURING REPRODUCTIVE TRANSITION
Authors: Meicenheimer Roger D.
Published: January 2018

The ontogeny of Epilobium hirsutum grown under natural summer photoperiod in a glasshouse was divided into vegetative, early transitional, transitional, and floral stages. Bijugate phyllotaxy, common to both the vegetative and early transitional stages, is transformed into spiral phyllotaxy during the transitional stage by an initial change in the divergence angle of a single primordium inserted at a unique level on the shoot. Leaf primordia subsequently are inserted in a spiral arrangement in the indeterminate floral shoot apex. The early transitional shoot apical meristem is about 1.5 times the volume of the vegetative meristem but expands at about two‐thirds the relative plastochron rate of volume increment of the vegetative meristem. There are progressive decreases in the plastochron and relative plastochron rates of radial and vertical shoot growth through ontogeny. Relative chronological rates of shoot growth, however, are not altered during ontogeny. Spiral transformation results from changes in the relative points of insertion of leaf primordia on the shoot meristem. These changes are accompanied by an increased rate of primordia initiation on a more circular shoot meristem. The change in phyllotaxy during ontogeny is similar to that which was artificially induced by chemical modification of auxin concentration gradients in the shoot apex, with the additional feature that there is an initial increase in the volume of the shoot meristem prior to the natural spiral transformation. Size of the shoot apical meristem, however, appears to have little influence on Epilobium phyllotaxy; but the geometric shape of the meristem is well correlated with bijugate to spiral transformations. This suggests that geometric parameters of the shoot meristem should be considered in theoretical models of phyllotaxy.
THE ULTRASTRUCTURE OF PALEOZOIC FERN SPORES: I. BOTRYOPTERIS
Authors: MILLAY M. A. , TAYLOR T. N.
Published: January 2018

The spores of four species of the Paleozoic filicalean fern Botryopteris are examined at the ultrastructural level. Spores of B. cratis, B. forensis, B. globosa, and an unnamed species from the Lower Pennsylvanian, are compared on the basis of sporoderm stratification and the presence or absence of a sculptine layer. The species examined differ widely as to the type of reproductive unit in which they are borne and include forms that range throughout the Pennsylvanian. In all species the exine is homogeneous, lacking cavities and lamellae. A thin nexine is present in the Middle and Upper Pennsylvanian taxa, but is absent in the Lower Pennsylvanian spores. Only one spore type (B. cratis) possesses a clearly defined sculptine layer. Features of the sporoderm are compared with those of extant, homosporous pteridophyte spores.
OBSERVATIONS ON P‐PROTEIN IN DICOTYLEDONS. SUBSTRUCTURAL AND DEVELOPMENTAL FEATURES
Authors: Arsanto Jean‐Pierre
Published: January 2018

The structure and development of P‐protein have been studied in sieve elements of hypocotyl tissue of Ecballium elaterium and Cicer arietinum, and in P‐protein‐producing cells of root apices of Polygonum fagopyrum. Ultrastructural investigations have led us to propose a model for the structure of P‐protein tubules. A tubule appears as a Super‐Double Helix (“DH1”) which consists of two 6‐ to 9‐nm‐diam strands wound round a central lumen, each strand exhibiting a varying‐pitched minor double helix (“DH2”). Our observations provide additional insights into the developmental relationships between the different forms of P‐protein and support the idea that spiny vesicles participate in P‐protein formation. The different types of P‐protein bodies found in mature sieve elements of species we have investigated may be regarded as arrays of axially oriented linked “DH1”
BIOLOGICAL EFFECTS OF SURFACTANTS. V. GROWTH AND ANTHOCYANIN PRODUCTION BY CALLUS CULTURES OF DIMORPHOTHECA
Authors: Ernst Robert , Ball Ernest A. , Arditti Joseph
Published: January 2018

Effects of five homologous series of amphoteric, anionic, and nonionic surfactants on growth and anthocyanin production by callus cultures of Dimorphotheca sinuata were examined. The phytotoxicity of amphoteric sulfobetaines increased with alkyl chain length and reached a plateau at 14 to 16 carbon atoms. In the case of the anionic sodium alkyl sulfates, the dodecyl derivative caused the greatest inhibition. Higher molecular weight ionic detergents were less toxic, probably due to their high Krafft temperatures and concomitant reduced solubility. The nonionic higher alcohol ethoxylates were generally less inhibitory than the ionic detergents and had little or no effect below their critical micelle concentrations. Fresh weights of tissues and anthocyanin production by Dimorphotheca callus cultures declined with increasing surfactant concentrations.
THE PROBLEM OF PLOIDY IN ECHEVERIA (CRASSULACEAE) II. TETRAPLOIDY IN E. SECUNDA
Authors: Uhl Charles H.
Published: January 2018

Every chromosome number from n = 12 to n =34 and also many higher numbers are known in one or more of the 130+ species of Echeveria, and the numerical boundary between diploids and tetraploids is not immediately apparent. Echeveria also is extraordinary for the number and diversity of hybrids that it can produce in cultivation, both within the genus and with species of several related genera. In 42 collections studied, the morphologically and cytologically variable E. secunda of central Mexico has n = 30‐32, often with one or more B‐chromosomes, and some quadrivalents are formed at meiosis in nearly every cell. Twenty‐four hybrids of E. secunda, with 22 species or cytotypes considered diploids, resemble the former much more closely in appearance, and at meiosis 15‐16 paired elements (bivalents and multivalents) are formed, never more, regardless of the number of chromosomes, 12 to 34, that were received from the other parent. It is concluded that the 15‐16 paired elements in these hybrids are formed by the 30‐32 chromosomes received from E. secunda, and that most chromosomes from the other parents occur as univalents, although usually a few associate with pairs from E. secunda to produce multivalents. Hybrids of E. secunda with 11 definitely tetraploid species having n = 34 to n = 68 are nicely intermediate in morphology between their parents, form mostly or entirely bivalents at meiosis, and most, probably all, including five intergeneric hybrids, are fertile. These observations are all consistent with the conclusion that E. secunda is an autotetraploid, even though no plants of the species having n = 15 or 16 have been found, and even though some other species of Echeveria having as many as 34 gametic chromosomes appear to be effectively diploid. Observations on pollen stainability and on second‐generation hybrids are all compatible with this conclusion. The high chromosome numbers in many Mexican Crassulaceae that are now effectively diploid may have originated as polyploids that have become diploidized by mutation, loss, or suppression of duplicated chromosomes, segments, and genes. Hybrids of E. secunda, with three other species that appear to be tetraploids, have less regular meiosis, apparently because all of the chromosomes from the other parents do not regularly form pairs in the hybrids. These three species may represent intermediate stages in the processes of diploidization.
SECONDARY GROWTH IN NEEDLE LEAVES OF PINUS LONGAEVA (BRISTLECONE PINE) AND OTHER CONIFERS: QUANTITATIVE DATA
Authors: Ewers Frank W.
Published: January 2018

Needle leaves of Pinus longaeva can be accurately dated and remain alive on branches for 30 or more yrs, making this species ideal to study secondary growth in leaves. Field observations and regression analysis of needle age versus mean needle length both indicate primary (elongation) growth of needles is completed in the first year. Statistical analysis of cell counts for one‐ to 33‐yr‐old needles indicate production along the entire length of needles of 1.0‐1.7 cell layers per year of secondary phloem, but no secondary xylem. Microscopic measurements and cell counts reveal that with advancing needle age phloem increases radially and transfusion tissue buckles, but the number of endodermal cells and xylem width do not change. Living phloem remains constant in amount (ca. 9 layers) with advancing needle age, indicating yearly replacement of old by new phloem. For comparison to P. longaeva, needle leaves were also studied for ten other conifer taxa with maximum needle longevities ranging from 3 to 19 yrs. In needles of each taxon no secondary xylem is produced, but secondary phloem production occurs throughout the post‐elongation lifespan of the needles regardless of maximum needle longevity.
GENETIC DIFFERENTIATION IN THE FLORIDA SUBSPECIES OF HELIANTHUS DEBILIS (ASTERACEAE)
Authors: Wain Richard P.
Published: January 2018

Techniques of horizontal starch gel electrophoresis were employed to estimate levels of genetic variation within and genetic differentiation among populations of the three Florida subspecies of Helianthus debilis. The subspecies are H. d. debilis, H. d. vestitus, and H. d. tardiflorus. These taxa are very similar with respect to levels of genetic variability. The average values across all populations for proportion of polymorphic loci (25.5%) and number of alleles per polymorphic locus (2.35) are comparable to those found in other outcrossing plants. The average frequency of heterozygotes per locus (0.05) is lower than that found in other outcrossers. Local populations within each subspecies are genetically very similar. The average genetic distance between local populations is D = 0.010 ± 0.001. Subspecies vestitus and subspecies tardiflorus are also genetically very similar (D = 0.015 ± 0.001). However, subspecies debilis is differentiated from both subspecies vestitus (D = 0.121 ± 0.006) and subspecies tardiflorus (D = 0.103 ± 0.005). This genetic differentiation parallels morphological differentiation. The average genetic distance among all three subspecies is D = 0.080 ± 0.003. A moderate amount of genetic differentiation accompanies the process of subspeciation in Helianthus debilis.
THE ONTOGENY OF THE INFLORESCENCE AND FLOWER OF LIQUIDAMBAR STYRACIFLUA L. (HAMAMELIDACEAE)
Authors: Wisniewski Michael , Bogle A. Linn
Published: January 2018

A developmental study of the inflorescence of Liquidambar styraciflua L. was conducted to clarify morphological discrepancies reported in the literature. Salient features of development are: 1) the inflorescence apex results from the conversion of a terminal, vegetative apex; 2) partial inflorescence apices arise as ellipsoid structures in axils of leaves, bracts, or transitional phyllomes; 3) development of male heads is acropetal whereas female heads differentiate basipetally; 4) the partial inflorescence apex becomes segmented into several distinct subunits indicating an axillary branch system of the third order; 5) distinct individual floral primordia are initiated on the subunits; 6) a complete absence of perianth development; 7) inception of carpel primordia in flowers of lower male heads as well as female heads, but a failure of the gynoecium to develop beyond an incipient stage in male heads; and 8) development of sterile structures around the base of the styles of only female flowers near the time of anthesis.

Carpellary characteristics of the sterile structures are described, their morphological nature is discussed, and the phylogenetic position of Liquidambar is evaluated.
STUDIES ON THE GERMINATION OF SEEDS OF THE ROOT PARASITES, ALECTRA VOGELII AND STRIGA GESNERIOIDES. I. ANATOMICAL CHANGES IN THE EMBRYOS
Authors: Okonkwo S. N. C. , Raghavan V.
Published: January 2018

Anatomical changes in the radicle and shoot meristems of embryos of germinating seeds of the obligate root parasites, Alectra vogelii and Striga gesnerioides were studied. When germination of seeds was stimulated by cowpea (Vigna unguiculata) root exudate, growth occurred mainly in the radicular pole of embryos and minimally in the plumular pole, resulting in seedlings with elongated radicles. Maximum radicle elongations of about 3 mm in A. vogelii and 2 mm in S. gesnerioides were recorded during a period of 8 and 11 days, respectively. Analysis of the radicular tip during the course of seed germination revealed that the activity of the meristematic tissue progressively decreased until it completely disappeared. When germinated seeds were cultured on nutrient agar media, the radicle meristem of A. vogelii continued to grow producing a normal root with a root cap. On the other hand, the radicles of cultured S. gesnerioides seeds elongated only slightly before meristematic activity ceased. During continued growth of seedlings of both species on agar media, lateral roots whose tips had typical angiosperm root topography, were initiated from the radicle.
AN INTRODUCTION TO MORPHOMETRIC CYTOLOGY AND ITS APPLICATION TO BOTANICAL RESEARCH
Authors: Toth Ronald
Published: January 2018

Morphometric cytology is the study which quantifies dimensions of cells and tissues through the observations of two‐dimensional sections. Useful parameters such as volumes, surface areas, numbers of particles, etc. can be determined from sections of plant materials. This paper introduces botanists to the basic concepts of morphometry as well as demonstrates their application. A section is included which outlines some of the pitfalls encountered in non‐random sampling of micrographs, artifacts due to shrinkage, section thickness, and specimen contrast. This article is designed to be a teaching tool which hopefully will stimulate botanists to apply these techniques in the future.
SHORT COMMUNICATION PETAL‐STAMEN INITIATION IN THE GENUS CYCLAMEN (PRIMULACEAE)
Authors: Sundberg Marshall D.
Published: January 2018

Petal‐stamen initiation was examined in nine species of Cyclamen. The pattern observed in all species is similar to that previously described in the commercial hybrid C. persicum ‘***F‐1 Rosemunde Rose‘: Stamens arise as adaxial outgrowths of common petal‐stamen primordia. This pattern differs from the characteristic “Primulaceous type” described in the literature. The correlation between the pattern of petal‐stamen initiation and phylogenetic specialization within the Primulales is discussed.
FURTHER EVIDENCE FOR OSMOREGULATION IN EPIDERMAL LEAF CELLS OF SEAGRASSES
Authors: Jagels Richard
Published: January 2018

A comparison of the epidermal leaf cell ultrastructure of three seagrasses, Thalassia testudinum (tropical, high salinity), Zostera marina (North temperate, moderate salinity), and Ruppia maritima (North temperate, brackish) provides confirmation for the theory that an invaginated plasmalemma‐mitochondrial transport system is developed at least in part as a response to salt concentration. Cytochemical localization of presumed Cl− ion provides further evidence for the presence of a salt secretion or exclusion mechanism.

Immature epidermal leaf cells communicate with each other and with mesophyll cells through numerous plasmodesmata, but during cell maturation these cytoplasmic connections are lost and the apoplastic transport system develops to replace the symplastic one. The two North temperate region seagrasses contain cytoplasmic lipids which are absent in the tropical species. Thalassia and Zostera have chloroplasts which lack starch, but stain densely for polysaccharides with thiocarbohydrazide. The polysaccharide staining is essentially negative in the chloroplasts of Ruppia, but mesophyll chloroplasts of this brackish water species contain starch. These and other cytological findings are compared with other seagrasses.
EXINE STRUCTURE OF TRICHOSPIRA VERTICILLATA (L.) BLAKE (COMPOSITAE) AND ITS IMPLICATIONS FOR THE TRIBAL POSITION OF THE GENUS
Authors: Bolick M. R.
Published: January 2018

Studies of the exine of Trichospira verticillata (L.) Blake reveal a modified Anthemoid (Liabioid) ultrastructural pattern linking the genus to the Vernonieae rather than the Heliantheae. This lends further support to Robinson and Brettell's transfer of the genus from the Heliantheae to the Vernonieae (Robinson and Brettell, 1973).
EUGLOSSINE BEE POLLINATION OF THE ORCHID, COCHLEANTHES LIPSCOMBIAE: A FOOD SOURCE MIMIC
Authors: Ackerman James D.
Published: January 2018

Cochleanthes lipscombiae is pollinated by large male and female euglossine bees. The flowers lack pollinator rewards, but attract bees searching for nectar. The euglossines extend their long tongues and crawl into the gullet‐flower. The bees probe the back‐swept lateral sepals for nectar. Pollination occurs as a pollinarium laden bee backs out, deposits pollinia on the stigma, and obtains a new pollinarium load by dislodging the anther. Some related orchid species have similar morphological characteristics as those essential to the pollination mechanism of C. lipscombiae. These features may have taxonomic significance at the generic level. Cochleanthes lipscombiae may be a floral mimic of a sympatric legume, but may also receive exploratory visits by bees searching for food resources. The latter may be young, recently emerged naive bees, or individuals seeking new nectar hosts during a period of rapid host species turnover.
INTERFERENCE BETWEEN INDIVIDUALS IN PURE AND MIXED CULTURES OF STEPHANOMERIA MALHEURENSIS AND ITS PROGENITOR
Authors: Gottlieb L. D. , Bennett J. P.
Published: January 2018

The diploid annual plants Stephanomeria exigua ssp. coronaria and S. malheurensis are related as progenitor and derivative. Stephanomeria malheurensis is known only from a single locality in eastern Oregon where it grows alongside (cohabits) its parent. Although the species are morphologically similar, they can be distinguished under uniform garden conditions by differences in root/shoot ratio, duration of rosette growth, branch structure and number of flower heads, seed weight, and other characters. The species were grown in pure and mixed cultures at several densities in two experiments to test the hypothesis that the distinctive phenotype of S. malheurensis could have evolved to reduce competition with its parent. The experiment revealed that the expression of the S. malheurensis phenotype did not change when it was grown alone or in mixed cultures with ssp. coronaria. Stephanomeria malheurensis neither gained nor lost an advantage. Since the measured characters related directly to fitness components, this suggests that the phenotype of the derivative probably did not evolve as a result of character displacement brought about by interference with ssp. coronaria. The consequence of sympatry between a newly arisen species and its parent appears to depend on the nature of the environment at the time of its origin. In an open habitat such as the Oregon locality of S. malheurensis, competition with the progenitor need not be a primary factor influencing the evolution of a new species.
A NATURALLY OCCURRING DEVELOPMENTAL SYNERGISM BETWEEN THE CELLULAR SLIME MOLD, DICTYOSTELIUM MUCOROIDES AND THE FUNGUS, MUCOR HIEMALIS
Authors: Ellison Aaron M. , Buss Leo W.
Published: January 2018

We here report the second record of a developmentally aberrant strain of a cellular slime mold from natural populations and demonstrate that this Dictyostelium mucoroides variant is capable of undergoing normal morphogenesis in the presence of the phycomycete fungus, Mucor hiemalis. The synergism is induced by an extracellular product(s) which is diffusable through thin agar membranes and is released by the fungus. The presence of the fungus not only induces stalk formation in this stalkless variant, but also increases the rate of sorocarp formation in 3 of 5 additional species of cellular slime molds assayed.
SUPERNUMERARY CHROMOSOMES IN SAXIFRAGA VIRGINIENSIS (SAXIFRAGACEAE)
Authors: Soltis Douglas E.
Published: January 2018

Acetocarmine squashes of root tips have demonstrated that 2n = 20 and 38 in Saxifraga virginiensis. These contrast with the earlier reported count of 2n = 28 for this species. In several populations supernumerary chromosomes were detected. Both intrapopulational and interpopulational variation in supernumerary chromosome number were detected, with the largest number of supernumerary chromosomes observed being six. Because these supernumerary chromosomes are equal in size to many of the smaller A chromosomes during mitotic metaphase, the presence of supernumerary chromosomes in this species could not be ascertained by analysis of mitotic metaphase preparations alone. During mitotic prophase, however, the supernumerary chromosomes of S. virginiensis are highly heterochromatic, appearing more densely coiled and darkly stained than the A chromosomes. This characteristic facilitated the recognition of supernumerary chromosomes in this species. The similarity in size of A and supernumerary chromosomes during mitotic metaphase and the observation of six supernumerary chromosomes in one population suggest that the count of 2n = 28 reported earlier for S. virginiensis may actually be a misinterpretation of 2n = 20 plus 8 supernumerary chromosomes. Furthermore, these findings and the observation of this same supernumerary chromosome phenomenon in other species of Saxifraga raise the possibility that some of the many disparate chromosome counts attributed to aneuploidy in the large genus Saxifraga may also be the result of misinterpretations of supernumerary chromosomes as A chromosomes.
GEOPERCEPTION IN PRIMARY AND LATERAL ROOTS OF PHASEOLUS VULGARIS (FABACEAE). I. STRUCTURE OF COLUMELLA CELLS
Authors: Ransom J. Steven , Moore Randy
Published: January 2018

Primary roots of Phaseolm vulgaris (Fabaceae) are positively geotropic, while lateral roots are not responsive to gravity. In order to elucidate the structural basis for this differential georesponse, we have performed a qualitative and quantitative analysis of the ultrastructure of columella cells of primary and lateral roots of P. vulgaris. Root systems were fixed in situ so as not to disturb the ultrastructure of the columella cells. The columellas of primary roots are more extensive than those of lateral roots. The volumes of columella cells of primary roots are approximately twice those of columella cells of lateral roots. However, columella cells of primary roots contain greater absolute volumes and numbers of all cellular components examined than do columella cells of lateral roots. Also, the relative volumes of cellular components in columella cells of primary and lateral roots are statistically indistinguishable. The endoplasmic reticulum is sparse and distributed randomly in both types of columella cells. Both types of columella cells contain numerous sedimented amyloplasts, none of which contact the cell wall or form complexes with other cellular organelles. Therefore, positive geotropism by roots must be due to a factor(s) other than the presence of sedimented amyloplasts alone. Furthermore, it is unlikely that amyloplasts and plasmodesmata form a multi‐valve system that controls the movement of growth regulating substances through the root cap.
CHLOROPLASTIC AND CYTOSOLIC ISOZYMES OF THE HOMOSPOROUS FERN ATHYRIUM FILIX‐FEMINA L
Authors: Gastony Gerald J. , Darrow David C.
Published: January 2018

Intact chloroplasts isolated from mature leaf tissue of the homosporous fern Athyrium filixfemina were osmotically ruptured and subjected to starch gel electrophoresis in side by side comparisons with whole leaf extracts. The single enzyme activities of reportedly cytosolic [NADP]IDH and [NADP]ME were not expressed in the chloroplast fraction, and these were used as controls ensuring the cytosol‐free quality of the chloroplast preparations. Isozymes F1,6DP‐1, PGI‐1, PGM‐1, 6PGDH‐1, ALDO‐1, TPI‐2, [NAD(P)]G3PDH‐1, and [NAD(P)]G3PDH‐2 are active in the chloroplast fraction, whereas Fl,6DP‐2, PGI‐2, PGM‐2, 6PGDH‐2, ALDO‐2, and TPI‐1 were lacking from the chloroplast fraction and are considered cytosolic. The single enzyme activities observed for AAT and SkDH, are chloroplastic. These data indicate that the two isozymes of certain enzymes in Athyrium filix‐femina are not the products of duplicated loci resulting from polyploidy, but are distinct and subcellularly compartmentalized as demonstrated in heterosporous plants. Thus A. filix‐femina is functionally diploid in spite of its high chromosome number of 2n = 80.
STABILITY OF A CHROMOSOMAL HYBRID ZONE IN THE CLARKIA NITENS AND CLARKIA SPECIOSA SSP. POLYANTHA COMPLEX (ONAGRACEAE)
Authors: Hauber Donald P. , Bloomaf2> William L.
Published: January 2018

Clarkia nitens and Clarkia speciosa polyantha (Onagraceae) are distinct chromosomal taxa differing by at least six reciprocal translocations. Where the taxa have come into contact, a chromosome boundary zone exists characterized by high levels of translocation heterozygosity due to at least 12 new chromosome arrangements which have evolved there. Previous studies have shown that these boundary arrangements are distributed such that they provide for full interfertility between adjacent populations. It was hypothesized that the geographic distributions of each of these arrangements will remain generally stable due largely to the very adverse effect that major changes would have on fertility. Evidence is presented here that over a ten year period the frequencies and geographic distributions of the chromosome arrangements within this boundary region have remained stable. The frequencies of the various chromosomal configurations (nine pairs, ring of four, two rings of four, ring of six, ring of four + ring of six, and ring of eight) from surveys in 1968 and 1978 have been analyzed statistically. In general, the analysis indicates that there have been no detectable changes over the 10‐yr period.
STUDIES OF CARBONIFEROUS FUNGI. II. THE STRUCTURE AND ORGANIZATION OF MYCOCARPON, SPOROCARPON, DUBIOCARPON, AND COLEOCARPON (ASCOMYCOTINA)
Authors: Stubblefield Sara P. , Taylor Thomas N. , Miller Charles E. , Cole Garry T.
Published: January 2018

The problematic organism, Sporocarpon, was among the first fossil fungi to be described. The genus was actually a heterogeneous assemblage of fungal forms, and was eventually divided into several taxa including Sporocarpon, Dubiocarpon, and Mycocarpon. In the present paper these organisms, as well as a similar, previously undescribed genus, Coleocarpon; are described from Lower, Middle, and Upper Pennsylvanian strata in North America, and from Upper Carboniferous sediments in England. Although initially considered to be radiolarian‐like protozoa, these structures show far more similarity to ascomycetous cleistothecia. All forms are ornamented, spherical bodies with a complex wall which encloses scattered asci and ascospores. Taxa are distinguished primarily by differences in the organization of the cleistothecial wall. Structurally similar organisms are found today among the Eurotiales.
THE POPULATION ECOLOGY OF A DUNE THISTLE, CIRSIUM RHOTHOPHILUM (ASTERACEAE)
Authors: Zedler Paul H. , Guehlstorff Kathleen , Scheidlinger Carla , Gautier Clayton R.
Published: January 2018

A population study of a thistle, Cirsium rhothophilum, was carried out in the coastal dunes of northern Santa Barbara County, California during 1978 and 1979. Seedling establishment, growth, flowering, and fruiting were observed in permanently marked transects. A total of 1,041 individuals were recorded. Despite 41% mortality during the year of study, the average population features changed remarkably little. Cirsium rhothophilum was found to be monocarpic but relatively long‐lived. Extrapolations from rosette size growth and proportions of rosettes in different size classes giving rise to flowering individuals suggest that the average plant may have a vegetative stage of more than 5 years. Growth analysis of c. rhothophilum is complicated by the subsurface branching of stems, presumed to be the result of insect damage and sand burial. Dissection of fruiting heads showed that sound achenes were only about 22% of the total number of potential achenes. Insect damage was evident on about 20% of the unsound achenes. Considering both the loss of achenes within heads and of entire heads which failed to mature, insects are estimated to destroy at least 25% of the achenes. Achenes germinate readily and do not appear to have more than mild dormancy. A burial experiment showed that emergence declined sharply with depth of burial to zero at 8 cm. Despite the dynamic nature of the dune habitat, C. rhothophilum populations appear stable. The relatively large size and ability to grow rapidly and adapt to burial allow C. rhothophilum to average out environmental vicissitudes.
IN SITU CERCIDIPHYLLUM‐LIKE SEEDLINGS FROM THE PALEOCENE OF ALBERTA, CANADA
Authors: Stockey Ruth A. , Crane Peter R.
Published: January 2018

Fossil seedlings and seeds of an extinct Cercidiphyllum‐like plant occur in the Paskapoo Formation (Late Paleocene) at Joffre Bridge near Red Deer, Alberta. Cotyledon and early seedling leaf stages are preserved in growth position. Morphological details of seedlings and seeds support a close relationship between the Paleocene fossils and extant Cercidiphyllum, and suggest that during the Upper Cretaceous and Tertiary (Paleogene) Cercidiphyllum‐like plants were important early colonizers of open flood‐plain environments.
N2(C2H2)ASE ACTIVITY BY ALNUS INCANA SSP. RUGOSA (BETULACEAE) IN THE NORTHERN HARDWOOD FOREST
Authors: Younger Patricia D. , Kapustka Lawrence A.
Published: January 2018

Field assays of N2(C2H2)ase activity were performed with intact nodules from a pure alder site (alder) and a mixed alder‐aspen site (aspen). Assays were performed between 12 June and 12 August 1980 and in May 1981. N2(C2H2)ase rates are expressed as g N g nodule oven‐dry wt−1 hr−1 (g N g−1 hr−1). Diurnal N2(C2H2)ase activity showed an increase in both sites between 0600 and midday, then decreased to a low by 1800. Nighttime activity in the May 1981 assay was approximately 25% of the daytime peak. Mean (±SE) 1200 hr N2(C2H2)ase activity (μg N g−1 hr−1) for all sizes in the alder stand rose from 24.56 ± 6.56 on 12 June to 73.96 ± 28.37 on 26 June and declined to 9.20 ± 2.56 by 12 August. In the aspen stand activity decreased from the 12 June rate of 21.81 ± 4.59 to 3.64 ± 1.87 on 24 July but then increased to 30.00 ± 7.39 by 12 August. Based on diurnal assays, the seasonal mean N influx (μg N g−1 hr−1) is statistically higher (P 0.05) in the alder stand with a value of 26.70 compared to 14.63 in the aspen stand. Small size class shrubs had significantly higher (P < 0.05) N2(C2H2)ase activity (μg N g−1 hr−1) in diurnal assays than medium or large class shrubs. The estimated mean (±SE) N2(C2H2)ase activity (mg N g−1 season−1) for all sizes was 44.4 ± 18.6 in the alder stand compared to 16.2 ± 5.2 in the aspen stand. Nodule excavations showed the g shrub−1 in the alder stand to be 16.48 ± 10.29, 38.57 ± 12.34 and 29.11 ± 7.15 for small, medium and large size shrubs and 12.73 ± 3.23, 28.21 ± 4.36 and 56.45 ± 16.23 for respective sizes in the aspen stand. Seasonal N influx was 4.69 kg ha−1 in the alder stand and 0.84 kg ha−1 in the aspen stand, representing 17.9% of the alder stand. Nitrogen feedback inhibition from uric acid‐N influx and allelochemic interference from aspen are discussed as explanations for the differences in N influx in the two stands.
PHLOEM OF PRIMITIVE ANGIOSPERMS. I. SIEVE‐ELEMENT ONTOGENY IN THE PETIOLE OF LIRIODENDRON TULIPIFERA L. (MAGNOLIACEAE)
Authors: Dute R. R.
Published: January 2018

As part of a continuing study of sieve elements in primitive angiosperms, a study of this cell type was undertaken in Liriodendron tulipifera. A typical ontogenetic sequence was observed in which synthetic processes such as wall thickening are followed in time by cellular lysis of nucleus, ribosomes, microtubules, vacuoles, and dictyosomes. This lysis is selective in that certain cellular components (e.g., the plasmalemma) remain unaffected. Concomitant with lysis is the formation of sieve‐area pores from plasmodesmata. Comparison of pore size on end and lateral walls indicates that the use of the term “sieve tube” rather than “sieve cell” to describe these elements is appropriate.
STRUCTURAL DEVELOPMENT OF THE CAUDICLE OF AN ORCHID (EPIDENDRUM)
Authors: Blackman Susan J. , Yeung Edward C.
Published: January 2018

Structural changes during development of the caudicle of Epidendrum ibaguense (Orchidaceae) were followed using light and electron microscopy. The caudicle begins as a mass of small meristematic cells in the microsporangium. The central cells of the mass enlarge and enter a division cycle. Completion of this cycle produces linear tetrads of cells which remain attached to each other throughout the life of the caudicle. These tetrads then accumulate a thick secondary wall on their outer surfaces. These thick‐walled cells form the main structural element of the caudicle at maturity. The cells on the periphery of the mass differentiate into a gradation of cell types characterized by their very high content of smooth ER. The majority of these thin‐walled cells are located at the junction points between adjacent caudicles and between caudicle and pollinium. The cells in these positions produce large quantities of a lipid polymer. This product is synthesized in association with large tubular ER complexes present in discrete areas in the cytoplasm. Plastids of these cells also produce a lipidic substance. Some thin‐walled cells are located among the thick‐walled structural cells; however, the lipid polymer is not synthesized in these cells. At maturity, all thin‐walled cells undergo breakdown and autolysis resulting in gradual obliteration of cytoplasmic detail and organelles. In the lipid containing thin‐walled cells, lysis of the cells releases the lipidic masses which then form the elastic joining compound between adjacent caudicles and between caudicles and pollinia.
SPIRAL TUBULES IN PALM PHLOEM
Authors: Norris Ronelle C. , Thomas Darryl L.
Published: January 2018

Spiral tubule structures were observed in sieve elements of Pritchardia and Cocos palms. The spiral tubules were 80–120 nm wide and composed of alternating electron‐lucent and electron‐dense bands 11–16 nm wide which spiraled around a central core.
OAK CATKINS, LEAVES AND FRUITS FROM THE OLIGOCENE CATAHOULA FORMATION AND THEIR EVOLUTIONARY SIGNIFICANCE
Authors: Daghlian Charles P. , Crepet William L.
Published: January 2018

Remains of staminate inflorescences, leaves, and fruits of Quercus from the Oligocene Catahoula Formation show striking similarity to modern subgenera Erythrobalanus (catkins and leaves) and Lepidobalanus (fruits). The appearance of modern subgenera in the Oligocene, only a short period of time after the first occurrences of Quercus in the fossil, record suggest a period of rapid evolution resulting in the modernization of Quercus. It is suggested that this period of relatively rapid evolution was in response to global climatic changes initiated at the Eocene‐Oligocene boundary that may have been exaggerated by an Oligocene global lowstand of sea level. The climatic deterioration induced by these events may have allowed Paleogene Quercus to enter new adaptive zones through migration and hybridization culminating in the final major modernization of the oaks.
THE REPRODUCTIVE BIOLOGY OF A RELICT–ILLICIUM FLORIDANUM ELLIS
Authors: Thien Leonard B. , White David A. , Yatsu Larry Y.
Published: January 2018

The flowers of Illicium floridanum are pollinated by a wide variety of insects, particularly Diptera that emerge from the litter and stream in early spring. Coleoptera rarely visit the flowers. It is suggested that the mode of pollination is ancient and may also exist in species of primitive angiosperms in the South Pacific. Illicium floridanum is self‐incompatible and possesses features of a gametophytically controlled incompatibility system. As a result of asexual reproduction, a lack of long‐distance dispersal of pollen and self‐incompatibility, fruit production is very low. This pattern of reproduction is found in other species of primitive angiosperms; incompatibility mechanisms which undoubtedly aided the angiosperms to become dominant may now be one of the major factors responsible for their extinction.
THE USE OF PROTEIN‐SEROLOGICAL CHARACTERS IN THE SYSTEMATICS OF THE FAMILY OLEACEAE
Authors: Piechura James E. , Fairbrothers David E.
Published: January 2018

Serological analyses of soluble seed proteins of 12 representative taxa of the family Oleaceae by the techniques of Ouchterlony, presaturation, and immunoelectrophoresis (IEP) yielded complementary taxonomic information. Ouchterlony reactions differentiated among protein extracts of three species, and the combined serological techniques permitted the detection of protein differences of respective taxa of the two subfamilies Jasminoideae and Oleoideae. IEP enabled the separation of the 12 taxa investigated and the distribution into the two subfamilies, by the differential electrophoretic positions of precipitin arcs, which were consistent with members of each of the two subfamilies. Presaturation data, when analyzed by two cluster analysis computer programs, were taxonomically significant. One program, which calculated amalgamation distances from the presaturation data, clustered the 12 taxa into subgroups which corresponded to tribes, and within two groups, which corresponded to two subfamilies. A monothetic clustering program provided theoretical information on evolution of taxa within the family Oleaceae based on serological correspondences obtained from the presaturation data; the subfamily Jasminoideae was found phylogenetically primitive and the subfamily Oleoideae was advanced. Additionally, IEP data supported those theories suggesting that taxa of the Oleoideae evolved from taxa of the Jasminoideae. The groupings of taxa and different information obtained from the cluster analyses of data and all serological techniques reinforced each other, as well as contemporary taxonomic and phylogenetic treatments of taxa of the family Oleaceae. This research demonstrated the taxonomic value of protein‐serological data, particularly as applied to the taxonomy of the Oleaceae.