xm LYCOPODINEsE 533 



half-grown, and by the time it has reached its full size the cell 

 divisions in the apical region are complete and the archegonia 

 have begun to form. (For details of the spore-development 

 in Selaginella see Fitting ( i ) ) . 



The ripe sporangium opens by a vertical cleft, as in Lyco- 

 podium. Goebel (22) has recently described in detail the 

 mechanism involved in the dehiscence of the sporangium. 



The Affinities of the Lycopodinece 



Among the living Lycopodineae there are two well-marked 

 series, one including the Lycopodiaceae and Selaginellaceae, the 

 other the Psilotaceae. In the first, beginning with Phylloglos- 

 sum, the series is continued through the different forms of 

 Ly co podium to the Selaginellaceae. The relation of the Psilo- 

 taceae to this series is doubtful, and must remain so until the 

 sexual generation of the former is known. The probable 

 saprophytic or parasitic life of these plants makes it impossible 

 to determine just how far their simple structure is a primitive 

 character rather than a case of degradation. 



Of the first series, it seems probable that of the forms whose 

 life history is known, the type of L. cernuum represents the 

 most primitive form of the gametophyte. It is reasonable to 

 suppose that in all these forms the prothallium was green, and 

 that the saprophytic prothallia, like those of L. phlegmaria and 

 L. annotinum, are of secondary origin. The prothallium, of 

 the type of L. cernuum, may be directly connected with the 

 Bryophytes and resembles them also in the small biciliate 

 spermatozoids, in which latter respect all the Lycopodineae yet 

 examined agree. This latter point is perhaps the strongest 

 reason for assuming that the Lycopods represent a distinct line 

 of development, derived directly from the Bryophytes, and not 

 immediately related to either of the other series of Pterido- 

 phytes. The character of the archegonium, as well as the long 

 dependence of the embryo upon the prothallium and the late 

 appearance of the primary root, point to the genus Lycopodium 

 as a very primitive type, even more closely related to the Bryo- 

 phytes than are the eusporangiate Ferns. Phylloglossuin, at 

 least so far as the sporophyte is concerned, is the simplest liv- 

 ing Pteridophyte. 



The close relation of Selaginella to Lycopodium is suf- 



