The structure & development of the mosses and ferns (Archegoniatae) . The first antheridia appear within three or four weeks underfavourable conditions, and are formed either from marginal orcentral cells of the prothallium. The very young antheridiumis scarcely to be distinguished from a young root-hair. Like it,it arises from a protrusion of the cell which is cut off by a wall,which is usually somewhat oblique. The papilla thus formedenlarges and soon becomes almost hemispherical. It containsa good deal of chlorophyll and a large central nucleus surroundedby dense cytoplasm. The first wall i
The structure & development of the mosses and ferns (Archegoniatae) . The first antheridia appear within three or four weeks underfavourable conditions, and are formed either from marginal orcentral cells of the prothallium. The very young antheridiumis scarcely to be distinguished from a young root-hair. Like it,it arises from a protrusion of the cell which is cut off by a wall,which is usually somewhat oblique. The papilla thus formedenlarges and soon becomes almost hemispherical. It containsa good deal of chlorophyll and a large central nucleus surroundedby dense cytoplasm. The first wall in the young antheridium 1 Cornu (i). - Prantl, Flora, 1S78, p. 499. FILICINE^ 311 (Fig. 157, A) is very peculiar. It has usually the form of afunnel, whose upper rim is in contact with the wall of theantheridium cell, and whose base strikes the basal wall of theantheridium. Sometimes this first wall does not reach to thebase, in which case it is simply more or less strongly concave,and the basal cell cut off by it from the antheridium is discoid. Fig. 157.—Oiioclea stritthiopteris {YioKm). Development of the antheridium. A-C, Vertical sections,x6oo ; D, two nearly ripe sperm cells ; E, free spermatozoid, X 1200 (about). instead of ring-shaped (Fig. 157, B). The second wall ishemispherical, and is nearly concentric with the outer wall ofthe antheridium. The dome-shaped central cell produces themother cells of the spermatozoids, and has much more densecontents than the outer cells, but all the chloroplasts remain inthe latter. A third wall now forms in the upper peripheralcell, much like the first one in form, and cuts off a cap cell at 312 MOSSES AND FERNS chap. the top. The young antheridium at this stage consists offour cells—a central dome-shaped one surrounded by threeothers, the two lower ring-shaped, and the terminal one outer cells are nearly colourless, and contain very littlegranular contents, except the small chloroplasts, which are
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