RICCIA. 83 



plant body has further specially organized chlorophyll- 

 bearing cells and protecting epidermal cells. Altogether 

 the plant is very much better organized for chlorophyll 

 work than is Coleochate. 



The sexual organs of Riccia are multicellular and 

 are nearly enclosed by vegetative tissues. They are not 

 imbedded when they begin to develop, but become so as 

 the adjacent tissues grow over them. The biciliate 

 sperms are discharged on the upper surface of the plant 

 and gain entrance to the egg through the canal of the 

 archegonium. 



After fertilization the egg does not pass through a 

 resting period, but soon begins to germinate without 

 being set free from the venter of the archegonium. It 

 develops a globular mass of cells, of which the outermost 

 layer produces no spores (i.e., it is sterile), but encloses 

 the spore-forming or sporogenous tissue within. This 

 sporogenous tissue finally forms a mass of heavy rough- 

 walled spores, that are eventually set free by the early 

 disappearance of the wall and ultimately by the decay 

 of the old plant body. At the return of favorable con- 

 ditions for growth these spores produce new Riccia 

 plants. 



It is evident that we have two kinds of spores formed, 

 one as the result of the union of the sperm and the egg, 

 and another as the result of development of this oospore. 

 One is sexual, the other asexual. The number of asexual 

 spores formed is quite large relatively, and serves very 

 greatly to increase the number of new plants that may 

 come from one oospore. The sporogonium, the structure 

 formed from the oospore, is, when ripe, little more than 



