. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. BRYALES 277 and the cblumella is in Andreaea a very irregular one (Fig. 135). Further, in Archidium, which some writers put in close relation to Andreaea, any cell derived from the endo- thecium may apparently become a spore- mother-cell. It is thus seen that though Sphagnum and 'Andreaea have certain apparent characters of the sporogonium in common, their segmen- tation is essentially different, and the dome- shaped archesporium is produced in different ways in the two. It remains doubtful there- for
. The origin of a land flora, a theory based upon the facts of alternation. Plant morphology. BRYALES 277 and the cblumella is in Andreaea a very irregular one (Fig. 135). Further, in Archidium, which some writers put in close relation to Andreaea, any cell derived from the endo- thecium may apparently become a spore- mother-cell. It is thus seen that though Sphagnum and 'Andreaea have certain apparent characters of the sporogonium in common, their segmen- tation is essentially different, and the dome- shaped archesporium is produced in different ways in the two. It remains doubtful there- fore how far the similarities indicate a real affinity. In any case the relation of the Andreaeales to the simpler Bryales is much nearer than to the Sphagnales, and it is in this direction that comparison of the sporo- gonia will bring the more interesting con- clusions concerning them. C. Bryales. These include the vast majority of Mosses. In their sporophyte generation there is uni- formity of the general scheme; though considerable fluctuation in size, as well as in minor detail. Some of the smallest forms, which show irregular opening of the capsule on maturity, are classed as the Cleistocarpae; the more elaborate forms, which dehisce transversely, setting free an operculum, are designated the Stegocarpae. The latter, as they represent the prevalent type in Mosses, will be taken first, while the Cleistocarpic forms being taken later, will then be better appreciated in their value for purposes of comparison. (a) Stegocarpae. The embryo of all these Mosses takes at an early stage the form of a more or less slender, but always simple spindle: any later deviations from this are of secondary origin. Its development from the zygote is first by the appearance of a transverse basal wall, which is succeeded by oblique segmentations in the epibasal half: these appear alternately on opposite. Ceratodon purpureus. A, B, young embryo seen from points of view at right angles to one another
Size: 993px × 2517px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisherlondonmacmillanand
