. The structure and development of mosses and ferns (Archegoniatae). himself admits, were in all casesembryos that had not fully developed. The writer has madea very complete examination of the commonest American spe-cies, N. orbicularis (valvata), and the results of the study of thedevelopment of the sporogonium differ so much from those ofLeitgeb that they will be given somewhat in detail. Mottier IV. THE ANTIIOCEROTES 149 (2) has also studied this species, and his results agree entirelywith those of the writer. The thallus much resembles a small Antlioccros, and sec-tions through it show th
. The structure and development of mosses and ferns (Archegoniatae). himself admits, were in all casesembryos that had not fully developed. The writer has madea very complete examination of the commonest American spe-cies, N. orbicularis (valvata), and the results of the study of thedevelopment of the sporogonium differ so much from those ofLeitgeb that they will be given somewhat in detail. Mottier IV. THE ANTIIOCEROTES 149 (2) has also studied this species, and his results agree entirelywith those of the writer. The thallus much resembles a small Antlioccros, and sec-tions through it show that in its growth and the developmentand structure of the sexual organs there is close thallus contains very large lacunae, which are formed inpretty regular acropetal order, and vertical sections show theselarge cavities increasing regularly in size as they recede fromthe apex. Similar but less regular lacunce occur in A. fiisifor-mis. The antheridia arise as in AntJwceros, youngest stage found is shown in Fig. 80, A. Here evi-. F\G. 80.—Notothylas orbicularis. Development of the antheridium. D, cross-section,the others longitudinal sections; E, nearly ripe antheridium, X300, the other fig-ures X600; (^, A, the primary antheridial cells. :%>mrto\fvi* ? . jrvA-f -? ;/^.t5l rj;t dently the young antheridia (c?) have been formed by the longi-tudinal division of a single hypodermal cell, whose sister epider-mal cell has divided again by a transverse wall to form the outerwall of the antheridiaTcavity (Figs. A, B). The commonestnumber of antheridia formed is four.~ r:^:.^n ?^^ i Less regularity is found in the next divisions than in AnfJio-ceros, although in the main they are the same. This is observ-able both in longitudinal and cross-sections (see Fig. 80, D). 150 MOSSES AND FERNS CHAP. The full-grown antheridium is more flattened than in eitherspecies of Anthoceros examined by me, and the stalk shorterand thicker, but otherwise closel
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