54 



MOSSES AND FERNS 



CHAP. 



there is a division of the outer of the two primary cells by a 

 wall parallel to the first, and that the lower one forms the foot 

 of the archegonium, and Janczewski ( i ) gives the same account 

 of the young archegonium of Pi'eissia commutata. This cer- 

 tainly does not occur in Targionia, and to judge from the later 

 stages of Fimhriaria Californica, this species too lacks this 



B 



Fig. i8. — Targionia hypophylla. A, Longitudinal section of the thallus, Xioo; ar, 

 archegonia; / /. ventral scales; B, median section through a pore, showing the 

 assimilating cells (c/) below, X300. 



division. The full-grown archegonium is of more nearly 

 uniform thickness than in Riccia, as the venter does not become 

 so much enlarged. The neck canal cells are more numerous, 

 about eight being the common number, but in Targionia the 

 formation of division walls between these is sometimes sup- 



