摘要:

At maturity the vascular cylinder of the stem ofLycopodium lucidulumcontains two distinct types of parenchyma cells, one which is always associated with sieve cells, the other with tracheids. The remaining parenchyma cells have characteristics intermediate between the two extremes. The most conspicuous feature of the sieve cell‐associated parenchyma cell is the very dense appearance of its protoplast, due to a high ribosome population and absence of large vacuoles. The large, ramifying nuclei of these cells have numerous connections with the endoplasmic reticulum (ER). The tracheid‐associated parenchyma cells, which are light in appearance, contain many small vacuoles and a relatively small ribosome population. These cells also contain relatively small nuclei and considerable ER cisternae. The parenchymatous elements which have characteristics intermediate between sieve cell‐ and tracheid‐associated parenchyma may or may not be contiguous to the sieve cells or tracheids. An intergradation in wall thickness occurs among parenchyma cells of the vascular cylinder, the thicker‐walled cells being adjacent to the sieve cells, the thinner‐walled ones next to the tracheids. An intergradation also occurs in the frequency of plasmodesmata between the various parenchyma cells. The closer parenchyma cells are to the sieve cells the greater the number of connections between them. No plasmodesmata were found between the tracheid‐associated parenchyma cells.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10781.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

The anomalous secondary wood ofA triplex confertifoliastems consists of vascular strands of xylem, phloem, and parenchyma embedded in fiberous conjunctive tissue. The included parenchyma contains chloroplasts and is capable of photosynthesis, as measured by14CO2uptake by wood in the light.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10782.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

The spermatozoids ofZamia integrifoliawere examined by electron microscopy in order to clarify the structure of a fibrous organelle underlying the flagellar basal bodies. The ultrastructure of this organelle was found to resemble one similar in organization occurring inMarchantiaspermatozoids and termed theVierergruppe.Therefore the term is extended to include this structure in theZamiaspermatozoid. The Vierergruppe ofZamiais interpreted as composed of an upper (distal) layer of keeled microtubules and a lower (proximal) layer of vertical fins with lateral processes that give a three‐layered appearance to this component.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10783.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Dormant seed and organs of 0‐, 1‐, 2‐, 5‐, 8‐, 11‐, and 14‐day‐old plants ofArachis hypogaeaL. were homogenized in phosphate buffer and the lipid‐free extracts analyzed for benzidine and pyrogallol peroxidases using starch‐gel electrophoresis. On a wet weight basis, one weak band of benzidine peroxidase activity was detected in dormant cotyledons and three bands in 1‐day cotyledons. In 5‐day tissue, activity had increased significantly; at 14 days, the number of bands had decreased but staining intensity was maintained. In the extract from dormant axis, a single cathodic site of benzidine peroxidase activity was observed; however, on day two there was a marked increase in the number of bands and intensity of reaction in epicotyl and hypocotylradicle tissues. By day 14, the number and density of bands had decreased noticeably in the epicotyl and hypocotyl. Extracts from 14‐day roots exhibited more sites of reaction and greater intensity of staining of benzidine peroxidase than at five days of growth. Localized areas of activity at Rf ‐0.44 and ‐0.52 were present in extracts of all four organs when either benzidine or pyrogallol was used as the hydrogen donor. Although marked similarity existed between banding patterns of organs, qualitative and quantitative ontogenetic differences in peroxidases were apparent.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10784.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Comparative studies of the nodal and vascular anatomy in the monotypic generaMetaxyaandLophosoriaare discussed as they relate to the taxonomy and phylogeny of the Cyatheaceae. Both genera are distinctive and primitive with respect to habit, stem and petiole indument, stelar pattern, and nodal anatomy.Metaxyapossesses a prostrate, dorsiventral rhizome, whereas a short, upright radial stem occurs inLophosoria.Trichomes occur on the stems and leaf petioles of these genera. BothMetaxyaandLophosoriahave a spiral phyllotaxy, and adventitious buds occur on the petiole bases. The stelar pattern is basically a siphonostele, although frequently a dictyostele is found inLophosoria.Accessory bundles are lacking in both genera. A characteristic petiole pattern is found in these genera, with an increase in complexity from an undivided strand inMetaxyato the three‐parted petiole pattern inLophosoria.Data from nodal and vascular anatomy indicate that these taxa are distinct from the other genera in the Cyatheaceae and belong in an independent position at the base of the Cyatheoid line, although in some respects an affinity to members of the Dicksoniaceae is indicated.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10785.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Vascular tissue development in the mature stems of the six squamate genera (those with scales as stem and petiole indument) of the Cyatheaceae is described. All squamate genera possess an erect stem, althoughCnemidariaapproaches an acaulescent condition. The majority of the species studied possesses a spiral phyllotaxy, although a whorled condition predominates in certain species. Adventitious roots arise from the leaf bases and, at irregular intervals, from the stem. Adventitious buds occur in the generaAlsophilaandNepheleaand show the same ontogenetic changes as occur in the young sporophytes of tree ferns. Mature stems have a dictyostele with overlapping leaf gaps; this consists of individual meristeles, each surrounded by sclerenchymatous tissue. All genera possess medullary bundles, whereas cortical bundles are found only in certain genera and species. The origin, course, and function of these accessory vascular bundles are discussed. The squamate genera in the Cyatheaceae show striking similarities in both anatomical and morphological characters, and constitute a natural grouping.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10786.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

The external spore morphology ofPhylloglossum drummondiiwas studied with the scanning electron microscope and shown to share a number of features with spores in the subgenusUrostachysinLycopodium.WithinUrostachysthe affinities ofP. drummondiiwere less evident: the foramino‐fossulate distal face, pyramidal proximal surface, and subcircular outline of its spores are similar to spores in the sectionPhlegmariawhile the weakly foveolate proximal surface and raised laesurae are characteristic of spores in the sectionSelago.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10787.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

A survey of pollen morphology in 20 species representing the 11 genera of the North American subtribe Stephanomeriinae by light, scanning electron, and transmission electron microscopy revealed 10 of the 11 genera to have echinate, tricolporate pollen grains,Lygodesmiabeing the only genus with echinolophate pollen. Sectioned exines of most of the species examined are similar, being composed of ektexine and endexine. The ektexine surface is composed of spines which typically have globose perforate bases. A cavus occurs as a separation between the basis (foot layer) and the columellae in all of the genera examined exceptChaetadelpha.Pollen of the two species ofGlyptopleurawere found to be strikingly different in exomorphology. Pollen of the putatively self‐fertileG. marginatahas much shorter spines than the closely relatedG. setulosa. Atrichoseris, Anisocoma, Calycoseris, Glyptopleura, Pinaropappus, Prenanthella, and most species ofMalacothrixhave pollen which lack paraporal ridges. The remaining genera,Chaetadelpha, Lygodesmia, Rafinesquia, andStephanomeriahave well‐developed ridges of fused spine bases around the apertures. Pollen characters, particularly those of the aperture region, have been found to be systematically useful in the subtribe, therefore acetolyzed material gives more useful information than untreated pollen.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10788.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Archegonium development, beginning with the archegonial initial and culminating in the mature egg, was studied with the electron microscope. The ultrastructural features of the beginning stages in development of the archegonium are relatively similar to one another. Plasmodesmata occur between all adjacent cells at this time. After the secondary central cell is formed these protoplasmic connections are lost, and both axial and parietal cell lineages begin to show signs of ultrastructural differentiation. The mature egg is characterized by cytoplasm rich in ribosomes and larger organelles. Mitochondria and simplified plastids commonly display a juxtaposed association. As far as could be ascertained the numerous plastids and mitochondria in the egg ofMarchantiaarise through division of preexisting organelles and are not formed anew from evaginations of the nucleus. Blebbing of the nucleus produces polymorphic organelles which appear to be pinched off into the cytoplasm. The mature egg also contains vacuoles and lipid bodies toward its periphery, while dictyosomes and extensive endoplasmic reticulum occur throughout. The space between the wall cells and the mature egg appears to contain an amorphous substance. No extra membrane was observed around the mature egg.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10789.x

出版商:Wiley    

年代:1974

数据来源: WILEY

摘要:

Spores of the true slime moldPhysarum polycephalumwere examined at several stages of their development by means of scanning and transmission electron microscopy. The spores were globose, spine‐covered structures produced within a sporangium enclosed in a tough, noncellular peridium. Cytologically, the spore represented a typical eukaryotic cell, having discrete organelles similar to spores of other myxomycetes. The presence of dictyosomes, helical filaments, and microbodies in these cells, as well as the further elucidation of the cell wall and the “polysaccharide‐containing” areas, represent new contributions to the ultrastructure of the myxomycete spore. Of special interest were observations of metaphase nuclei just prior to spore cleavage, interphase nuclei in young spores, and nuclei in mature spores containing synaptonemal complexes. These observations indicate that inPhysarum polycephalummitosis occurs just prior to spore cleavage, and meiosis takes place after spore cleavage.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1974.tb10790.x

出版商:Wiley    

年代:1974

数据来源: WILEY