. The structure and development of mosses and ferns (Archegoniatae). ^ -^ Fig. 127.—Botrychiitm Virgiyiianum. A, B, Germinating spore, X6oo; C, pro-thallium {pr), with young sporophyte attached, X2; D, longitudinal section of theprothallium, showing the foot of the embryo (F), X4; E, first (?) leaf of ayoung sporophyte, X2. As the prothallium grows older—it may evidently live forseveral years—it becomes irregular in outline. It may finallyreach a length of twenty millimetres, and occasionally shows in-dications of a dichotomy of the apex. Sex-OrgansThe first antheridia form a small group upon
. The structure and development of mosses and ferns (Archegoniatae). ^ -^ Fig. 127.—Botrychiitm Virgiyiianum. A, B, Germinating spore, X6oo; C, pro-thallium {pr), with young sporophyte attached, X2; D, longitudinal section of theprothallium, showing the foot of the embryo (F), X4; E, first (?) leaf of ayoung sporophyte, X2. As the prothallium grows older—it may evidently live forseveral years—it becomes irregular in outline. It may finallyreach a length of twenty millimetres, and occasionally shows in-dications of a dichotomy of the apex. Sex-OrgansThe first antheridia form a small group upon the upper sur-face of the prothallium while it is still very young. The laterones form only upon the median ridge already referred to. 240 MOSSES AND FERNS CHAP. Still later the archegonia appear along the base of the anther-idial ridge (Fig. 126, B). The development of the antheridium (Fig. 128) is muchlike that of Ophioglossum, but the outer wall of the antheridiumhas normally two layers of cells. The spermatozoids, accord-ing to Jeffrey, probably correspo
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910