63 



All these changes have gone on in the spore, the 

 early ones while the spore was in the sporangium, 

 and the later ones after the dissemination of the 

 spores. The outer cuticularised wall bursts soon 

 after the archegonia begin to appear, the prothallium 

 is liberated and slightly protrudes ; the three con- 

 vergent edges burst lengthwise and form a three- 

 rayed fissure. At the apex the first archegonium is 

 in process of development. 



FEETILIZATION. 



This mast take place in water. The walls of the 

 Antherozoid mother cells become disorganised, and 

 the antherozoids are set free. They show active 

 movement and swim away by means of their cilia. 

 Their movement after liberation lasts from thirty to 

 forty- five minutes. A drop of mucilage exudes from 

 the archegonium — the antherozoids swim about aim- 

 lessly till they come within microscopic distance of 

 an archegonium. They approach the opening, 

 become entangled in the mucilage, and screw and 

 wriggle down the canal until they reach the ovum. 

 One antherozoid fuses with the nucleus of the ovum, 

 and fertihzation is effected. 



Changes after Fertilization. 



(1) The ovum secretes a cell wall. 



(2) Division by a transverse wall takes place. 



(3) One of these cells elongates, and forms the 

 suspensor, which gives rise to a number of 



