292 



GENERAL BOTANY 



In the alga this cell usually passes through a resting period, 

 after which it germinates to form a new filamentary plant, 



or gametophyte. 



In Ricciocarpus the 

 zygote becomes an 

 embryo plantlet, or 

 sporophyte, through 

 cell division and cell 

 differentiation, as in 

 the higher plants 

 already studied, but 

 in the embryo of 

 Ricciocarpus cell di- 

 vision and differen- 

 tiation are limited, 

 and so the resulting 

 sporophyte plant is 

 relatively simple, as 

 we have seen. 



The sporophyte 

 of Ricciocarpus evi- 

 dently corresponds 

 in the life history 

 to the embryo and 

 the adult plant of 

 the bean or the man- 

 drake, since they are 

 all derived by simi- 

 lar processes from 

 an initial fertilized 

 egg cell, or zygote. 

 Plants like Riccio- 

 carpus and the man- 

 drake, which have a sporophyte plant alternating in the life 

 history with the gametophyte plant, are said by botanists to 

 have an alternation of generations in the life cycle. 



FIG. 162. Habit of a moss, showing the leafy game- 

 tophytes and sporophytes. After Sachs 



