74 



the canal cell. The canal cell in Aspidium does not 

 undergo any division, but it always contaiDS four 

 nuclei, arranged one underneath each other. When 

 this stage is reached, the canal cell with its four 

 nuclei, and the ventral canal cell with its single 

 nucleus, become disorganised and form a mass of 

 mucilaginous material which absorbs water with 

 eagerness. This causes the stigmatic cells, i.e.^ the 

 uppermost four of the neck cells, to split apart and 

 so the neck is opened. The archegoniuni is now ready 

 or fertilization. 



Fertilization, This must take place under water. 

 The antherozoids are liberated at about the same time 

 that the necks of the archegonia are opened, The 

 antherozoids are chemically attracted hj the malic 

 acid contained in the mucilage, are caught in large 

 numbers, and wriggle and screw down the neck. 

 During this operation they lose their cilia and ves- 

 icles. The one that reaches the nucleus of the ovum 

 first is absorbed, and fertilization is effected. 



Fertilization may thus he defined ai the quickening of 

 the ovum hj means of the nuclear lody of an antherozoid. 



EESULTS OF FERTILIZATION. 



The protoplasm surrounding the nucleus convul- 

 sively contracts, and acquires a cell wall. The fol- 

 lowing changes are constant in Aspidium : — 



1. The nucleus divides into two, and a ceU 

 wall is developed parallel to the long axis of 



