摘要:

SUMMARYElectron microscopy has clarified the structure and taxonomic position of the genusMesostigma(type speciesM. virideLauterborn) by showing that the two unequal flagella are covered with small scales of a characteristic shape and that they arise from a conical pit in the upper surface of the cell which is lined by a dispersed system of tubes or fibres as in the related genusPyramimonas. The periplast over the rest of the cell is shown to contain two other very distinct kinds of scales which are described. The origin of all three types of scale has been traced to vesicles derived from Golgi cisternae, and scale liberation though not traced in detail is believed to take place into the flagellar depression. The peculiar flattened shape of the chloroplast with restriction of starch storage to a swollen border, the structure of the pyrenoid and the distribution within the cell of other cell components is also indicated in outline. It is concluded that though unique in many respects the genusMesostigmais unequivocally a member of thePrasinophyceae(sensuParke&Manton, 1965) and is relatively remote from theVolvocalesin which it was formerly classed.

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1965.tb00056.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe substance of this paper opened the symposium on ‘Structure and functioning of apical meristems’ at the X International Botanical Congress, Edinburgh, 1964. It is a review, but includes original work onMacrozamia communis.The works of Hanstein (the so‐called ‘Histogen Theory’ of 1868), Duliot (1890) and Schmidt (the ‘Tunica‐Corpus Theory’ of 1924) are compared and shown to be descriptively similar. Their term ‘initia’ l, in regard to any one layer or to the central region of the apex or to the whole apex (gymnosperms), corresponds to the ‘apical cel’ l in regard to the whole apex of pteridophytes.Thecontinuing meristematic residue(i.e., the apical cell or cells) is proposed for a line (or lines) of cells inheriting the office of initial. Derived from this, thegeneral meristemis the site of elaboration of primary tissues. In both components of the apical meristem no cell is permanent. Three basic types of continuing meristematic residue (i.e., monoplex, simplex and duplex apices) may have phylogenetic‐taxonomic significance. Seed plants are interpreted as having ‘apical cells’, not pyramidal, not necessarily single, and not always superficial.Histological differences between ‘reproductive’ and ‘vegetative’ shoot apices are paralleled by differences between vegetative apices during different growth performances, and may be merely growth differences preceding or accompanying reproduction.Macrozamia communissupplies an original example.Root apices may be grouped in at least five types according to tissue derivation, with no major taxonomic significance, and distributable among the three basic types of continuing meristematic residue.A ‘quiescent centre’ (not completely inactive) is regarded as inevitable and not diminishing the significance of initial (apical) cells.The significance of primary augmentive meristem is discussed, and the primary thickening meristem is exemplified by original observations onMacrozamia communis.The following principles are applied to several features in the literature: (1) distinction between continuing meristematic residue and general meristem; (2) pattern being in fixed relation to the advancing apical surface; (3) no cell being a permanent cell in the meristem.The paper concludes with an attempt to indicate the paths

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1965.tb00057.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1965.tb00058.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1965.tb00059.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1965.tb00060.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY