144 THE NATURE AND WORK OF PLANTS 



fuse with the female gametes, as m the fern, and the 

 cell formed germinates without leaving its place as 

 in the fern, but the structure of the individual 

 formed is very much different. The second genera- 

 tion consists of a slender brownish or greenish stem, 

 bearing a large capsule. This capsule is composed 

 of tissue which contains chlorophyl, is furnished 

 with a hood or other appendages, and contains a 

 flask or sac, the contents of which develop into 

 spores. The spores germinate and form the leafy 

 stemmed plants examined at first, and the capsule 

 and its stalk are thus the sporophyte of the moss. 

 It is seen to be able to form some of its food by 

 means of its chlorophyl, but it is dependent upon 

 the gametophyte for its supply of water and mineral 

 salts, and is sometimes said to be parasitic upon it. 



199. Occurrence of generations. — This alterna- 

 tion of the two generations of a species is not inva- 

 riable. It was found that by vegetative methods 

 of reproduction (§ 180) the cutting reproduces its 

 own generation in all the experiments tried. There 

 are some instances, however, where the cutting of a 

 sporophyte will produce a gametophyte, and vice 

 versa. Then, again, the spores developed by the 



