. The structure and development of mosses and ferns (Archegoniatae). l cells, the antheridium resembles that of Gleich- THE HOMOSPOROUS LEPTOSPORANGIAT^ Z77 enia. In the Hymenophyllaceae no cap cell is formed, but as inOsmunda and Gleichenia, the upper cell is divided by wallsrunning over the apex. The divisions in the central cell andthe structure of the spermatozoids, so far as these have beenstudied, correspond with those of the other single archegonial cushion is not formed, but the arche-gonia occur in small groups at different points upon the (lo) has sh
. The structure and development of mosses and ferns (Archegoniatae). l cells, the antheridium resembles that of Gleich- THE HOMOSPOROUS LEPTOSPORANGIAT^ Z77 enia. In the Hymenophyllaceae no cap cell is formed, but as inOsmunda and Gleichenia, the upper cell is divided by wallsrunning over the apex. The divisions in the central cell andthe structure of the spermatozoids, so far as these have beenstudied, correspond with those of the other single archegonial cushion is not formed, but the arche-gonia occur in small groups at different points upon the (lo) has shown, however, that these archegonial groupsarise first near the growing point of the prothallial branch, andthat they are simply separated by the intervention of zonesof sterile tissue. At the point where they arise the prothalliumbecomes more than one cell thick, and in all cases where thedevelopment could be certainly followed, the archegoniumarose from one of the ventral cells, and never directly from amarginal cell. The details of the development have not been. Fig. 2i8.—Part of the filamentous prothallium and archegoniophores of Trichomanesrigidum. (After Goebel.) followed, and whether there is any division of the neck canalcell is not known. The neck is straight, as in Osmunda andGleichenia. In Trichomanes the archegonial meristem (archegonio-phore) may be formed as a short branch, directly upon the fila-mentous prothallium. The lateral walls of the prothallial cells are in all the speciesthicker than is the case in most Ferns, and there are distinct pitsin them. In the rhizoids a parasitic fungus is frequentlyfound. The embryogeny is almost unknown (Janczewski (2) ), butthe first divisions and the very young sporophyte correspond 378 MOSSES AND FERNS CHAP. closely with those of the other Leptosporangiatae. The coty-ledon is simple with a single median vein, and a root is presentin all species yet examined. The Mature Sporophyte Prantl (i) has given a very complete acco
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