ALTERNATION OF GENERATIONS 



321 



When the moss is covered over with water, it is possible for the male 

 gametes to swim about, and some of them find their way into the 

 archegonium. Here one of the sperm cells fuses with the egg cell, 

 and the fertilized egg cell begins to develop into a new moss plant 

 immediately that is, while still within the body of the parent. 



FIG. 149. Alternation of generations in the life history of the moss 



G, the gametophyte, or gamete-bearing plant ; /, the female gamete organ ; m, the male 

 gamete organ ; e, the fertilized egg resulting from the fusion of egg and sperm ; S, the 

 sporophyte, or spore-bearing plant ; s, spores. The spore always develops into a gameto- 

 phyte ; the gametes (egg) always give rise to a sporophyte. G and S represent alternate 

 generations that reproduce in different ways, the first sexually, by means of gametes, 

 the second asexually, by means of spores 



But the new plant is very different from the parent plants. It has 

 no leaflike organs or anything to correspond to leaves. It consists 

 mainly of stalk, and at its base it is buried in the tissues of the parent 

 plant, from which it gets most of its nourishment. It is therefore 

 parasitic upon the parent to a large extent. At the end of the stalk 

 a capsule is formed, and when this is ripe, a great many spores are 



