Ill 



THE JUNGERMANNIALES 



the formation of a second apical cell in one of the youngest 

 segments. This apical cell is formed by a curved wall, which 

 strikes the outer wall of the segment (Fig. 37, C). Thus 

 two apical cells arise close together, and as segments are cut 

 off from each, they are forced farther and farther apart, and 

 serve as the growing point of two shoots, which may continue 



FIG. 39. Aneura pinnatifida. A, Part of a thallus with two antheridial branches, 

 slightly magnified; B, an archegonial branch, X4o; C, cells from the margin of 

 the archegonial branch showing the oil bodies (0), X3oo. 



to grow equally, when the thallus shows a marked forking 

 (M. furcata), or one of the branches grows more strongly than 

 the other, which is thus forced to one side and appears like a 

 lateral branch (Aneura pinnatifida, Fig. 41, B). 



In certain species of Pallavicinia and Symphyogyna, and 

 especially in Hymenophyton (Fig. 38, B), the gametophyte 

 .shows a differentiation into a prostrate rhizome-like steri, 



