222 General Biology 



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

 tinguished from the adult plant which, as we have seen, is called the 

 sporophyte. 



There is an asexual multiplication of sphagnum also. This is 

 brought about by a sterile branch which develops more powerfully than 

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

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

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

 pendent 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 



I I 



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 



Spore Spore Spore Spore ' Reduction 



I 

 Protonema 



I 



Thallus 



I 



Sphagnum-plant (gametophyte) 



The so-called true mosses (Fig. 109) have life-histories quite like 

 that of sphagnum, although there are differences. In true mosses the 

 protonema produces leafy branches (the true moss-plants), but it does 



