PLANT WORLD CONTINUED 221 



spore until the thallus develops, is the gametophyte. This is to be distin- 

 guished from the adult plant which, as we have seen, is called the sporo- 

 phyte. 



There is an asexual multiplication of Sphagnum also. This is 

 brought about by a sterile branch developing more powerfully than the 

 surrounding ones. Then, each year, as the old stern dies off below, 

 the young branch becomes a new plant. Sometimes little plantlets, 

 known as innovation branches (Fig. 117), strike root and be- 

 come independent plants. These innovation branches spring from close 

 to the tip of the sterile branches. 



The life-cycle of Sphagnum may be summarized as follows : 



OUTLINE OF LIFE HISTORY OF SPHAGNUM 



Sphagnum-plant (gametophyte) 



Antheridial branch Archegonial branch 



I I 



Antheridia Archegonia 



1 1 



Sperm (male gamete) Egg (female gamete) 

 Fertilization 



I I 



Oosperm (zygote) 



I I 



Embryo 



I I 



Mature Sporophyte 



I I 



Sporangium 



I I 



Spore-mother-cell 



c c ~ f Reduction 



Spore Spore Spore Spore ) 



I 

 I 



Protonema 



I 



Thallus 



I 



Sphagnum-plant (gametophyte) 



