178 A TEXT-BOOK OF BOTANY 
moss plant, which does not produce spores, but which does 
produce sex-organs, is the gametophyte generation in the 
life-history. It is plain that the ciliated sperms are organ- 
ized for swimming, and that fertili- 
zation can take place only when there 
is sufficient moisture for this purpose. 
A 
Fic. 172.—Developing sporophyte of amoss: A,young F1¢.173.—A common moss- 
sporophyte developed from egg in archegonium; bearing mature sporo- 
B and C, more advanced stages, in which the phytes, which are long- 
sporophyte is elongating and hecoming anchored stalked spore - cases. — 
in the leafy plant.—After GorsBeL. After ScHENCK. 
