. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. BRYALES 283 Phascum: the sterilisation of the whole of the upper products of the endothelium at the narrow distal end of the fertile tract would interrupt the dome, and complete the columella, just as it is seen in Phascum. There is no inherent im- probability in this, but rather the reverse: for it would be only introducing one further step in sterili- sation. On such grounds the relation of the Phasca- ceae to the Andreaeaceae would appear to be a near one. Another simple Cleisto- carpic form which
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. BRYALES 283 Phascum: the sterilisation of the whole of the upper products of the endothelium at the narrow distal end of the fertile tract would interrupt the dome, and complete the columella, just as it is seen in Phascum. There is no inherent im- probability in this, but rather the reverse: for it would be only introducing one further step in sterili- sation. On such grounds the relation of the Phasca- ceae to the Andreaeaceae would appear to be a near one. Another simple Cleisto- carpic form which has not only been observed exter- nally, but also worked out developmentally, is Nano mitrium tenerum. The small capsule has here a provision for dehiscence by the formation of a rudimentary annulus. The segmentation of the embryo begins on the plan of the Bryales (Fig. 140, 1.), and there IS as USUal a differen- Phascum cusfiidatum, Schreb. Schut. .4= longitudinal section .... r,i 1 , - through a sporogonium after formation of the air-space; j/=arche- tiatlOn 01 tue enuOtneClUm sporium; sps=spore-sac; jeg=limits between amphithecium and âj _* ..i â /rv endothecium. £=transverse section of the same. (After Kienitz- and amphithecium (Fig. Gerioff.) 140, 11.). The cells of the latter, after further division, become differentiated into an exiguous central columella, surrounded by relatively numerous and somewhat irregularly arranged spore-mother-cells (Fig. 140, iv.): but as maturity approaches the columella disappears, its materials having served for nourishing the spores which fill the cavity of the capsule. The genus Ephemerum is closely related with that of Nanomitrium, from which it differs in the absence of any definite operculum: the condition of the columella is the same, but while it disappears at maturity in some species (E. papillosum), in others it may still be seen in the mature capsule (E. crassinervium). The fact that stomata occur on the capsule-wall, though w
Size: 1386px × 1803px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherlondonmacmillanand
