. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 288 MOSSES AND FERNS CHAP. arrangement, both of the divisions of the leaf and the venation. This is brought about in both cases by an unequal dichotomy, by which one branch develops more strongly than the other, so that the lattet appears lateral. With the assumption of the pinnate form the leaf also develops the wings or appendages upon the axis between the pinnae. In the fully-developed leaves of the mature sporophyte, the last trace of this is seen in the ultimate branching of the veins, wh
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. 288 MOSSES AND FERNS CHAP. arrangement, both of the divisions of the leaf and the venation. This is brought about in both cases by an unequal dichotomy, by which one branch develops more strongly than the other, so that the lattet appears lateral. With the assumption of the pinnate form the leaf also develops the wings or appendages upon the axis between the pinnae. In the fully-developed leaves of the mature sporophyte, the last trace of this is seen in the ultimate branching of the veins, which is always dichotomous. The second root arises close to the base of the second leaf, and at first there seems to be one root formed at the base of each of the young leaves; in the older sporophyte the roots are. Fig. 160.—A, Longitudinal section; B, transverse section of roots from older sporo. , phyte of M. Douglasii, showing apparently more than one initial cell, X200. more numerous. Holle states that this is not the case in Marattia, where only one root is formed for each leaf, in Angiopteris two. This, however, requires confirmation in the older plants. As the roots become larger it is no longer pos- sible to distinguish certainly a single initial cell. The adjacent segments themselves assume to some extent the function of initials, and thus in place of the single definite apical cell a group of apparently similar initials is formed, which takes its place (Fig. 160). This seems to be in some degree associated with the increase in size of the roots.^ ' It is possible that a single initial may be present even here, but the great similarity of the central group of cells makes this exceedingly difficult to Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Campbell, Douglas Houghton, 1859-1953.
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
