LIFE HISTORY OF A LIVERWORT 



223 



previously studied. Except for the sterile wall-cells, all 

 the cells formed by the successive divisions of the oopserm 



FIG. 169. Ricciocarpus. sp., sporogonium; gam, tissue of gametophyte. 



FIG. 170. Life cycle of Ricciocarpus. (After Cardiff.) 



become spore-mother-cells, each of which, by the tetrad- 

 division, gives rise to four spores. Meanwhile the wall- 



