. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. Ill THE JUN GERM ANN I ALES 103 what unequal size. The next wall formed divides the larger of the two primary cells into an inner and an outer cell (Fig. 50, A), so that the young segment now consists of three cells, an inner one and two outer; the latter in the dorsal segments correspond to the two lobes usually found in the dorsal leaves. The two outer cells now divide by walls in two planes, and rapidly grow out above the level of the apical cell and form. Fig. 50.—Porella Bolanderi. A, Med
. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. Ill THE JUN GERM ANN I ALES 103 what unequal size. The next wall formed divides the larger of the two primary cells into an inner and an outer cell (Fig. 50, A), so that the young segment now consists of three cells, an inner one and two outer; the latter in the dorsal segments correspond to the two lobes usually found in the dorsal leaves. The two outer cells now divide by walls in two planes, and rapidly grow out above the level of the apical cell and form. Fig. 50.—Porella Bolanderi. A, Median longitudinal section of a vegetative axis; B, a cross-section of the apex of a similar one, X500; x, the apical cell; h, hair; d, dorsal surface; v, ventral surface; C, male; D, female branch. lamellae which remain single-layered, and undergo but little further modification beyond an increase in size. From the base of the young leaves simple hairs develop, but remain small and inconspicuous. The inner of the three first formed cells of the segment, by further division and growth in all direc- tions, produces the axis of the plant. This in cross or longi- tudinal section shows almost perfectly uniform tissue. No distinct epidermis, or central strand, like that found in most Mosses, can be 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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