. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. THE BRYALES 223 Bastit ((i), p. 295), who has made a compar- ative study of the subter- ranean and aerial stems of P. juniperinuni, divides the outer tissue of the lat- ter into epidermis, hypo- derma, and cortex. In the subterranean stems he finds the construction quite different from that of the leafy branches. The section of the former is triangular, and its epi- dermis provided A\ith hairs which are absent from the epidermis of the aerial parts. Rudimen- tary scales, arranged in three rows
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. THE BRYALES 223 Bastit ((i), p. 295), who has made a compar- ative study of the subter- ranean and aerial stems of P. juniperinuni, divides the outer tissue of the lat- ter into epidermis, hypo- derma, and cortex. In the subterranean stems he finds the construction quite different from that of the leafy branches. The section of the former is triangular, and its epi- dermis provided A\ith hairs which are absent from the epidermis of the aerial parts. Rudimen- tary scales, arranged in three rows, are present, and corresponding to these are strands of tissue that represent the leaf- traces of the aerial stems. The central cylinder is much larger relatively than in the leafy branches, and its cross-section is not continuous, but is inter- rupted by three "pericyclic sectors," composed of cells whose walls are but little thickened. The point of each sector is at the periphery of the me- dulla, or central cylinder, and the broad end toward the centre. As might be expected, intermediate con- ditions are found where the rhizome begins to grow. >cl Fig. 121.—A, Transverse section of the leaf of Leucobryum; B, similar section of the leaf of Polytrichum commune; cl, chlorophyll-bear- ing cells (after Goebel). upward to forrn a leafv branch,. 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. New York, The Macmillan Company;
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