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 



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 scores. 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 gametopkyte t 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- 



