342 



MOSSES AND FERiYS 



CHAP. 



cases there is a true dichotomy (Fig. 171, A). Slender 

 filamentous prothallia are especially common in this species 

 (Fig. 172, C), and recall somewhat those of some species of 

 Trichoniajtes . 



The prothallia of the Osmundaceae often form adventitious 

 buds, much like those of the Marattiaceae. These secondary 



A. 



Fig. 171. — A, Apex of a young prothallium of O. Claytoniana, with two similar initials, x, x , X 560 ; 

 B, longitudinal section of an advanced prothallium of O. cinnamomca, X260; C, horizontal 

 section of a similar one, showing two initials, X 260. 



prothallia (Fig. 172, B) generally arise from the margin, but 

 may be produced from the ventral surface. An apical cell is 

 usually early established, and the subsequent growth is closely 

 like that of the primary one. 



The prothallia are long lived if they remain unfertilised, and 

 Goebel ^ states that in O. regalis they may reach a length of four 



1 Goebel (16), p. 199. 



