ASPIDIUM GAMETOPHYTE 315 



absolute alcohol, a method which gives very good 

 results. The preparations described below may also be 

 made from fresh material, but the results will not be 

 nearly so good as if one of the above methods of fixing 

 and hardening be adopted. 



Hold a prothallus thus prepared between pieces of 

 pith, or embed as directed on p. 11 : then cut sections 

 perpendicularly to the surface of the prothallus, and so 

 as to pass through the cushion, following the organic 

 axis from base to ajpex. Mount in glycerine, and 

 examine first with a low power. 



The lower surface may easily be recognized by the 

 presence of root-hairs : on this lower side, chiefly 

 near to the apical end of the section, which is charac- 

 terized by its small cells with thin walls, will be found 

 archegonia : these may be recognized by the multi- 

 cellular neck, which projects beyond the surface of the 

 section. In some cases the canal of the neck may 

 appear of a deep brown colour : this is the case in old 

 archegonia which have not been fertilized, and they 

 must be disregarded. Select one archegonium of full 

 size and healthy appearance, and examine it under a 

 high power. 



Observe that it consists of 



A. The central series of three cells, which may be 

 distinguished as 



a. The canal-cell : this is oblong in form, and its 

 walls are subject to mucilaginous degeneration : it 

 occupies the channel of the neck, and has been above 

 alluded to as being visible when the neck of the 

 archegonium is seen from above. 



b. The small ventral canal-cell, which lies imme- 



