摘要:

Gametophytes and embryos ofActinostachys wagneri, A. pennula, andSchizaea elegansare described along with a few observations on those of 5.dichotoma, A. digitata, A. spirophylla, Ophioglossum pendulum, Danaea simplicifolia, Botrychium virginianum, B. dissectum, andPsilotum nudum.Variation in the gametophyte and embryo at the interspecific level within the Schizaeaceae is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14055.x

出版商:Wiley    

年代:1975

数据来源: WILEY

摘要:

The fine structure of primary, secondary, and tertiary stages ofZeaendodermal cell development was investigated. The casparian strip formed in situ in the anticlinal walls and remained at a fixed point relative to the endodermis‐pericycle boundary. The only protoplasmic structure that had a constant spatial association with the developing strip was the plasmalemma. Plasmodesmata appeared to be more numerous on the tangential walls than on radial walls; only rarely were they located in the casparian strip. The suberized lamella developed on inner and outer tangential walls before it appeared on the radial walls. No cytoplasmic organelles were found to have any particular spatial association with this layer. The suberized lamella was about 0.04 μm thick except near plasmodesmata and along the adaxial margin of the casparian strip, where it was thicker. Occasionally it failed to form along the abaxial margin of the strip. The adherent affinity between plasmalemma and casparian strip was lost after the strip was covered by suberized lamella. The secondary wall became asymmetrically thickened by differential deposition of successive lamellae. A thin layer of secondary wall material extended across the floor of each pit. Pit cavities often contained mitochondria, and plasmodesmata were restricted to the pits. The plasmodesmata were constricted where they entered the thin layer of secondary wall material and where they penetrated the suberized lamella. The various stages of cell development tended to be asynchronous. No passage cells were observed. Endodermal cell development inZeaclosely resembles that described for barley.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14056.x

出版商:Wiley    

年代:1975

数据来源: WILEY

摘要:

Vegetative nuclear divisions in cystosoral Plasmodia from the shoot system ofSorosphaera veronicaeSchroeter were studied with standard transmission electron microscopy. Each metaphase nucleus forms a cruciform configuration as the persistent nucleolus elongates perpendicularly to chromatin aligned on the equatorial plate. The nuclear envelope remains intact during metaphase and anaphase. Each spindle pole consists of a fenestrated nuclear envelope with an exteriorly situated centriole and closely associated endoplasmic reticulum. Intranuclear membranous vesicles occur within metaphase and anaphase nuclei and are closely associated with chromatin and nuclear envelope. Microtubules pass from centrioles into the nucleus and are also attached to chromatin at kinetochores.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14057.x

出版商:Wiley    

年代:1975

数据来源: WILEY

摘要:

GlomerisporitesandAriadnaesporitesare two genera based on megaspores and microspores from the late Cretaceous. Each has megaspores with characteristics shared with other late Cretaceous Salviniaceae, including numerous floats, an acrolamella, and a complex perispore. Microspores are borne singly, however, not in characteristic salviniaceous massulae. Microspores ofGlomerisporiteshave a pseudovacuolate basal region and a single spore in an apical neck. Microspores ofAriadnaesporitesare structurally like the megaspores but of smaller size.Ariadnaesporites variusoccurs in the Cenomanian Stage (early late Cretaceous) and is the oldest presumed member of the Salviniaceae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14058.x

出版商:Wiley    

年代:1975

数据来源: WILEY

摘要:

Phycomyces blakesleeanus(Burgeff) produces both giant and dwarf sporangiophores from superficial and submerged hyphae. The morphogenesis of submerged primordia has been studied in cultures grown in petri dishes on a defined nitrogen‐poor medium at low temperature under varied conditions of illumination. The primordia of dwarf and giant sporangiophores differed markedly in size, morphology, tropistic behavior, developmental plasticity, photosensitivity, and conditions required for initiation. Dwarf primordia, abundant only in dark‐grown cultures, began as hyphal thickenings that later developed characteristic ramifications not seen in giant primordia. The formation of dwarf primordia was correlated spatially and temporally with termination of mycelial expansion near the rim of the dish and in local regions elsewhere. Illumination strongly suppressed the ramification process in existing primordia but did not prevent the maturation of dwarf sporangiophores that had already emerged from the nutrient surface. Giant primordia were prominent only in illuminated cultures. With continuous light from the time of inoculation, giant sporangiophores and giant primordia were found chiefly in midregions of the dish. If illumination was delayed until dwarfs had begun to form near the rim of the dish, the giant primordia were also concentrated near the rim. In that case about half of the giants were formed by conversion of a small fraction of the existing dwarf primordia and the rest were formed de novo from vegetative hyphae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14059.x

出版商:Wiley    

年代:1975

数据来源: WILEY

摘要:

Astragalus cibariusandA. utahensisare common perennial species of a widespread legume genus. The pollination ofAstragalushas been briefly discussed in the literature, but little work has been done on species in the intermountain West. This study was conducted from 1970–1973 in Utah with mixed and single species populations. The flowers of both species were homogamous and papilionaceous, but the species were different as to color, size, and ultraviolet reflectance.Astragalus cibariususually flowered 10 days ahead ofA. utahensis, but both species flowered earlier than most other plants in the community. Bagging experiments indicated both species were strongly allogamous. Exclosure studies indicated both species relied on insects as pollen vectors. Of the 44 insect species which were observed visiting flowers, only 14 carriedAstragaluspollen, and the pollinator fauna varied between study sites. Pollen quantities and distributions on Diptera and Coleoptera indicated a poor potential for pollination. Floral structure, pollen distribution and quantity, and behavior implied that large bees of the families Apidae and Anthophoridae were the primary pollinators. These bees visited only one species ofAstragaluswhen the plants occurred in mixed populations; this constancy may have been related to relative flower abundance. Non‐pollinating floral foragers affect other phases ofAstragaluslife history.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14060.x

出版商:Wiley    

年代:1975

数据来源: WILEY

摘要:

Comparisons of variations of morphological features, treated quantitatively, of the megagametophytic stages inCornus asperifoliaMichaux., C.strictaLam.,C. amomumMiller,C. floridaL., andC. alternifoliaL. suggest differences in growth patterns of their megagametophytes. The successful application of the clearing fluid 41/2 (Herr Fluid) affords adequate data for assessment of quantitative features of such minute plants. This method, less time consuming than traditional paraffin sectioning techniques, allows for statistical treatment of a sufficient number of species for valid inferences of angiospermous embryological features. An investigation of megagametophytic size was directed both to successive stages within each species and to each stage among all five species. In both instances, means, confidence intervals (CI), and growth increments (GI) were compared. Without exception, the largest means for length and width occurred in the 8‐nucleate stage for all species. The greatest GI for length occurred in the 8‐nucleate stage forC. stricta, C. alternifolia, and C.asperifoliaand in the 4‐nucleate stage forC. florida.The 4‐ and 8‐nucleate GI were nearly equal forC. amomum.Overlapping of 95 % CI between successive stages indicated uniform growth between stages for the megagametophyte. OnlyC. asperifoliahad CI overlapping between all successive stages for length and width. These five species are clearly separated on the basis not only of variations in qualitative features but also on megagametophytic growth patterns among species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14061.x

出版商:Wiley    

年代:1975

数据来源: WILEY

摘要:

Although the unique tissue required for C4photosynthesis in nonsucculent plants is often described as being modified leaf parenchyma sheath, which is positioned meaningfully between the mesophyll externally and the vascular tissues internally, the actual range of locations and known associations make that concept untenable. In origin the Kranz tissue develops from procambium as well as ground parenchyma. It is found in stems as well as leaves. In position Kranz tissue can lie in the parenchyma sheath, in the mestome sheath, isolated in the mesophyll, peripherally in some thick leaves, or within the veins. It can be associated with mesophyll only, mesophyll and colorless parenchyma, mesophyll and sclerenchyma, other Kranz tissue and vascular tissues, mesophyll and mestome sheath, mesophyll and phloem, mesophyll and xylem, epidermis, and, finally, mestome sheath and xylem and phloem. The use of the term Kranz is expounded.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14062.x

出版商:Wiley    

年代:1975

数据来源: WILEY

摘要:

The fine structure of mesophyll chloroplasts in green islands and in adjacent chlorotic areas of barley leaves infected withErysiphe graminis(DC.) was compared with healthy non‐inoculated tissue. Chloroplasts in green islands were persistent. Green‐island chloroplast grana were enlarged and fewer in number than in healthy tissue. In contrast, cells in chlorotic areas had fewer chloroplasts and their lamellae showed progressive degeneration and fragmentation. The lamellae often resembled aberrant prolamellar bodies. As lamellar degeneration progressed there was a marked increase in the amount of osmophilic material within the chloroplasts.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14063.x

出版商:Wiley    

年代:1975

数据来源: WILEY

摘要:

Equisetum clarnoiis described from four silicified stem fragments and numerous small roots from the Eocene Clarno Chert of Jefferson County, Oregon. Stems are up to 8.0 mm in diam and have sunken stomata arranged vertically in a single line flanking each of the external biangulate stem ridges, features that clearly ally this species with the subgenusHippochaete.External stem ridges are equal in number to the carinal hypodermal bands. The hypodermis is composed of fibers and has prominent carinal bands up to 0.75 mm long and shorter vallecular bands. Cortical parenchyma cells enclose prominent vallecular canals which are lined by specialized thick‐walled parenchyma cells. The double, common endodermis has prominent casparian strips. Vascular bundles are composed of four to seven metaxylem tracheids flanking each side of the phloem and protoxylem tracheids which occur singly on the internal surface of the small carinal canals. Leaf sheaths in cross section have an adaxial fibrous layer and an external or near external fibrous bundle. Roots are up to 2.0 mm in diam and have paired cuboidal epidermal cells from which root hairs arise. The stele of the root is central and shows exarch primary xylem maturation.Equisetum clarnoimost closely resembles the extantEquisetum hyemalevar.affine.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1975.tb14064.x

出版商:Wiley    

年代:1975

数据来源: WILEY