.' c:ji;i.-l, as he uui'uu inc eiisoc in ioiv;''-- I. 

 grov;''^'ii iuid division of tlie primary spo.-tmo;inm mother cells, 

 v/hicii j-o-Ti thus al'.:o bi.c ultiniate sporLinp:i'-im motiior cells. 

 A stalk cell is f o -med in i]\e dGvelopnent O- ti\o micro- 

 spor.-uigiiim, but no'iJiing iionioiogous v/ith this xni'z seen in 

 'he case of the macrosporanginm. Tlie indusium of each 

 sorus arises pai'tl^' v/ith.in its o n sc^jment, buu partly 

 also from the next older segment. It ir; derived from the 

 dermatogen cells of sections II oXiu V anu ironi tlie mar- 

 ginal cells. The gelatinizing tissue of the dorsal part 

 of the capsule arises largely, if not entirely, from the 

 plerome of section II ; that of the ventralside from th.e 

 dermatogen of s ctions II and V , and tliat at either 

 end of tho capsule probably comes from all three meristem 



.ayers. 



Conclusions. 



Tlie leaf of fersilia agrees closely with those of 

 most of tlie leptosporangiat;. Ferns v/hich have been stud- 

 ied, in its origin, in its grov/th by a two sided apical 

 cell, and in the development of the lamina by the contin- 

 ued activity of the marginal ceils of ceKr.in of its 

 segments. Tlie position of the primary or section walls 

 in the segments of the leaf, v;hile agreeing closely witli 



