90 



MOSSES AND FERNS 



CHAP. 



In the ordinary form four sets of segments are cut off, — dorsal 

 and ventral, as in Riccia or Sphcerocarpus, and two sets of 

 lateral ones. In Pellia calycina the apical cell shows a similar 

 form, but in P. epiphylla (Fig. 42, D, E), another type is 

 seen. Here, while the surface view is the same as in P. caly- 



B. A 



Fig. 41.— a, Pallavicinia cylindrica, X4; per, the elongated perianth; B, Aneura pin- 

 natiUda, X6; J, archegonial branches; C-E, Fossombronia longiseta, X4; F, Blasia 

 pusilla, X4. 



cinaj in vertical section the cell is nearly semicircular, i. e., here 

 there are but three sets of segments, two lateral ones and a 

 basal one, extending the whole depth of the thallus, and only 



