LIVERWORTS: RICCIA. 



225 



All the inner cells, which are richer in protoplasm, divide into 

 four cells each. Each of these cells becomes a spore with a thick 

 wall, and is shaped like a triangular pyramid whose sides are of 

 the same extent as the base (tetrahedral). These cells formed in 



B 



Fig. 255- 



Nearly mature sporogonium of Riccia crystallina ; 

 mature spore at the right. 



Fig. 256. 



Riccia glauca ; archegonium 

 containing nearly mature spo- 

 rogonium. sg, spore-producing 

 cells surrounded by single layer 

 of sterile cells, the wall of the 

 sporogonium. 



fours are the spores. At this time the wall of the spore-case dis- 

 solves, the spores separate from each other and fill the now en- 

 larged venter of the archegonium. When the thallus dies they 

 are liberated, or escape between the loosely arranged cells of 

 the upper surface. 



481. A new phase in plant life. Thus we have here in the 

 sporogonium of riccia a very interesting phase of plant life, in 

 which the egg, after fertilization, instead of developing directly 

 into the same phase of the plant on which it was formed, 

 grows into a quite new phase, the sole function of which is the 

 development of spores. Since the form of the plant on which the 

 sexual organs are developed is called the gametophyte, this new 

 phase in which the spores are developed is termed the sporo- 

 phyte. 



Now the spores, when they germinate, develop the gameto- 

 phyte, or thallus, again. So we have this very interesting condi- 



