CHAP. XI THE HOMOSPOROUS LEPTOSPORANGIAT.K 



339 



has an exceedingly delicate endospore, which is difficult to 

 demonstrate, but after the exospore bursts along the three 

 ventral ridges, and the endospore is exposed, it becomes 

 very evident. 



The first division takes place after the spore has elongated 

 slightly, and is usually transverse, separating the small root-hair 



sp D. 



Fig. 169. — Osmunda Claytotiiana (L.). A, Ungerminated spore ; i, ventral surface ; 2, optical 

 section, x 550 ; B, germinating spores, X275 ; r, primary rhizoid ; C-E, older stages, X275 ; sp, 

 spore membrane ; .r, apical cell. 



from the large prothallial cell (Fig, 169, B). The young root- 

 hair contains chlorophyll, but not so much as the larger cell. 

 As germination proceeds the chloroplasts separate and increase 

 in size. They are often arranged in lines extending from the 

 large nucleus to the periphery of the cell. As a general thing, 



