20S PRACTICAL BOTANY. 



sections perpendicularly to the surface of the pro- 

 thallus, and so as to pass through the cushion, following 

 the organic axis from base to apex. Mount in one part 

 glycerine and one part water, and examine first with a 

 low power. 



The lower surface may easily be recognised by 

 the presence of root-hairs, and on this lower side, 

 chiefly near to the apical end of the section which is 

 characterised by its small cells with thin walls, will be 

 found Archegonia ; these may be recognised by the 

 multicellular neck, which projects beyond the surface 

 of the section. [N.B. In some cases the canal of the 

 neck may appear of a deep brown colour : these are old 

 archegonia which have not been fertilised, 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. A 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. 



I. The small Ventral Canal-cell, which lies imme- 

 diately below the oblong canal- cell, and is of rounded 

 form. 



c. The Oosphere, which is of relatively large size, 

 and roughly spherical form ; it is embedded in the 

 tissue of the cushion, and consists of a dense mass of 

 granular protoplasm. 



