48 



(5) Each spore mother cell gives rise to four spores 

 in the following way : — 



i. The nucleus divides into two and each of 

 these into two, so that four nuclei are 

 formed, sometimes all in one plane and 

 sometimes in two planes. 



ii. Two cell walls are developed in such a 

 way that each of the four cells thus 

 produced has its own nucleus. 



iii. The protoplasm collects round each nucleus, 

 and the outer layer of each mass is converted 

 into cellulose. The investing cell walls 

 become disorganised, and the spores are 

 free in the sporogonium. 



(6) In the meantime, from the base of the arche- 

 gonium is developed aD investing coat called 

 the Perigynium, which surrounds the archegon- 

 ium as a sac. 



(7) The Sporogonium is now ripe, the seta 

 elongates rapidly, this ruptures the calyptra 

 and the sporogonium protrudes. The calyptra 

 surrounds the base of the seta as a cup-like 

 membranous structure. 



(8) The wall of the sporogonium ruptures irregu- 

 larly, and the spores are liberated. The 

 elaters, which are strongly hygroscopic, bend 

 to and fro with the changes in the atmosphere^ 

 and so assist in the dissemination of the spores. 



