THE HOMOSPOROUS LEPTOSPORANGIAT^ 



375 



and the tip is cut off by a transverse wall from the basal cell- 

 In the terminal cell are next formed a series of vertical walls, 

 which transforms it into a row of cells extended at right angles 

 to the axis of the pedicel. One of the central cells now bulges 

 out laterally, and this papilla is cut off by an oblique wall and 

 forms the beginning of a short lateral branch, so that the fully- 

 developed bud has somewhat the form of a three-rayed star, 

 and in this condition becomes detached and grows into a new 

 prothallium. The prothallia formed in this way often do not 



Fig. 216.— Hymenophyllum (sp). Margin of a prothallium with numerous gemmae k; 

 X85; B, a young gemma, X260; st, its stalk. 



develop a flat thallus, but may remain filamentous, and each 

 ray may produce antheridia either terminally or laterally (Fig. 

 215, C). In case a flat thallus is formed, only one or some- 

 times two of the rays grow out in this form, the other having 

 only a limited growth, and terminating in a short rhizoid. In 

 short, the process is very similar to that in the germinating 

 spores. 



