2 24 STRUCTURE AND LIFE HISTORIES 



cells become disorganized and their substance goes to nour- 

 ish the spores. By this time the cells of the inner layer 

 of the venter have also become disorganized and their sub- 

 stance, in like manner, is absorbed by the spores (Fig. 169). 

 Thus the tissue of the gametophyte serves as nourish- 

 ment for the developing, primitive sporophyte. The phe- 

 nomenon of an embryo developing into a mature sporophyte 

 is practically eliminated. As we descend the scale of plant 

 life we find the sporophyte becoming simpler and simpler; 

 and this simplicity consists in the diminution of the amount 

 of sterile tissue. 



204. Life History of Riccia. — The Kfe history of Riccia 

 is shown in outline as follows, and diagrammatically in 

 Fig. 170. Carefully compare this history with that of 

 Anthoceros. 



OUTLINE OF LIFE HISTORY OF RICCIA 



Riccia-plant (gametophyte) 



I 



Antheridia Archegonia 



4, I 



Sperms Egg 



Oosperm (zygote) 

 Cell-divisions 

 Sporophyte (transient spore-case) 



Spore-mother-cells 



\- \. 4, 4' J Reduction 



Spore Spore Spore Spore 



i 



Protonema 



Riccia-plant {gametophyte} 



