. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. Fig. 24.—Targionia bypophylla. A, Median longitudinal section of older embryo enclosed in the calyptra (cflO> X80; B, a portion of the upper part of the same embryo, X480; the nucleated cells represent the archesporium; C, part of the archesporium of a still later stage; et^ elaters; sp, sporogenous cells, X480. In the latter the wall becomes later more definite, and remains but one cell thick until maturity. The arrangement of the cells of the archesporium is very irregular, and until the

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. The structure and development of mosses and ferns (Archegoniatae). Plant morphology; Mosses; Ferns. Fig. 24.—Targionia bypophylla. A, Median longitudinal section of older embryo enclosed in the calyptra (cflO> X80; B, a portion of the upper part of the same embryo, X480; the nucleated cells represent the archesporium; C, part of the archesporium of a still later stage; et^ elaters; sp, sporogenous cells, X480. In the latter the wall becomes later more definite, and remains but one cell thick until maturity. The arrangement of the cells of the archesporium is very irregular, and until the full number of these is formed they are all much alike. Just before they separate, however, careful observation shows that two well- marked sorts of cells are present, but intermingled in a perfectly irregular way A part of these cells are nearly isodiametric, the others slightly elongated, and the nuclei of the former cells. 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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