摘要:

At a stage in ontogeny while they are still held together in tetrads, but before the formation of the exine, the microspores ofSelaginella brooksiiHieron. show features of the cell surface which suggest that material is being taken up by pinocytosis. These features, which are confined to the proximal face of the spore, are: (1) cytoplasmic fringes which arise near, arch over and enclose membrane‐bound particles on the cell surface, (2) invaginations of the plasma membrane which form smooth‐surfaced vesicles, and (3) invaginations of the plasma membrane to form coated vesicles. The membranes which limit all three kinds of vesicle are asymmetrical. Sections that cut the surface of the microspore tangentially at or in the vicinity of this surface activity show a hexagonal lattice which is a surface specialization possibly connected with pinocytosis. There are indications that the pinocytosed material is digested by lysosomal enzymes; myelin‐like residual bodies are formed which migrate to the periphery of the cell. These observations are discussed in relation to the nutritional explanation of heterospory in the pteridop

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1974.tb01617.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The history of the taxonomic perception ofEucalyptus globulusLabill. is described. Morphological‐geographical clusters withinE. globulusare identified through the use of a polythetic, agglomerative classificatory strategy. The results of the numerical analysis and unpublished data on geographic variation strongly suggest that four subspecies should be recognized. Thus three taxa formerly regarded as species are reduced to subspecies ofE. globulu

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1974.tb01618.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The shape of the cotyledon lamina and a few other juvenile characters are studied for some 140 taxa of the cruciferous tribe Brassiceae. They cast a number of doubts on the present botanical status of certain taxa, such asDiplotaxis siifolia, Erucastrum cardaminoidesandBrassica balearica.The whole tribe Raphaninae appears rather unnatural when viewed from cotyledon evidence, which suggests that beak development and/or fruit reduction have evolved on different occasions. A primitive cotyledon type seems to be that showed by the genusSinapidendron.It is nowadays still present inBrassica balearica, Oudneya africanaand the oriental genusOrychophragmus.Some phenetic lines now represented byMoricandia, Foleyola, Hemicrambe, DiplotaxisandBrassica repandamay indicate ancient evolutionary trends derived from the primitiveSinapidendron‐likeMiocenic stock.Brassicaancestors could have either resembledB. repandaor evolved along the phenetic line now represented by theDiplotaxis Erucastrum‐Brassicacomplex. A diphyletic or polyphyletic origin for the genusBrassicabecomes thinka

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1974.tb01619.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Buds removed from herbarium specimens were processed for light microscopic examination of colleter form and anatomy. MostPavettaspecies have dendroid colleters and bacterial leaf nodules, a correlation also found in an earlier study ofPsychotria.Colleters ofNeorosea, another genus with leaf‐nodulated species, are more like the standard rubiaceous type that predominates in the family except that they have irregular, bulging epidermal cells.Tricalysia, a nodule‐free genus closely related toNeorosea, shows a range of colleter form from standard to dendroid, and some species have theNeoroseatype of colleter. Such morphological correlation between the bacterial leaf nodule symbiosis inPavettaandPsychotriaand dendroid colleters may indicate a chemical change in colleter secretion. Apart from their involvement with the bacterial symbiosis, rubiaceous colleters have now been shown to vary sufficiently in certain taxa to be considered as additional useful taxonomic charact

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1974.tb01620.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The stomata ofGinkgo bilobaL. are haplocheilic and perigenous, as described and confirmed by Pant&Mehra in 1964, but there are several striking differences in the structure of the stomatal apparatus between their descriptions and the findings recorded in the present paper. According to the present observations, the stomata are amphicyclic (usually incompletely), not monocyclic as they stated. There are 5 to 7 subsidiary cells (not 4 to 6); and a clear distinction into lateral and polar subsidiary cells is visible during most of the developmental stages at least, a fact that was not mentioned by Pant&Mehra. The papillae of the subsidiary cells arise from the outer free walls, not from the inner (centripetal) walls as they claimed. Further, these papillae do not conceal the stomatal pore as completely as was indicated previously: they extend only partially towards the opening of the epistomal chamber. These and other differences from published accounts are dealt with briefly and commented upon in the paper. Some notes are also included on the occurrence of amphistomatic leaves, and on the occurrence and nature of twin stomata.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1974.tb01621.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The structure and distribution of transfusion tissue in the leaves ofCunninghamia lanceolatahas been studied. It is made up of tracheids, albuminous cells and parenchyma. The tracheids occur to the right and left of the vascular bundle, while the albuminous cells are lateral to the phloem and the parenchyma is principally in the adaxial and abaxial positions. The transfusion tissue, therefore, appears to be distributed all round the vascular bundle and not only lateral to it as was reported in the earlier descriptions.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1974.tb01622.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY