118 



STRUCTURAL BOTANY 



repeatedly by transverse walls, so that the ripe 

 archegonium consists of a chimney-like neck, enclosing 

 a row of canal- cells leading down to the ovum at the 

 bottom (see Fig. 54). The cap-cell at the top of the 

 neck divides into four by vertical walls crossing each 

 other at right angles. We see that the archegonium of 



a Liverwort differs 

 from the corre- 

 sponding organ 

 of a Fern or other 

 Vascular Crypto- 

 gam, not only in 

 the much greater 

 length of the neck, 

 but also in the 

 origin of the neck- 

 canal. In the 

 Liverworts this is 

 derived from the 

 upper part of the 

 archegonium ,while 

 in the Vascular 



The youngest stages are shownjn Crypfcoganis it is 



the venter, neck, and canal are clearly 

 shown. 0, ovum ; V. C. C, ventral canal- 

 cells. Magnified about 200. 



FIG. 54. Archegonia of a Liverwort (March 

 antia). The youngest stages are sho^ 

 the left. In the more mature arche. 



formed from an 

 outgrowth of the 

 central cell. The 

 final result, however, is much the same in both cases, 

 and on the whole there is more reason to lay stress on 

 the essential similarity of the sexual organs in plants so 

 remote from each other, than to dwell on their somewhat 

 minute differences. 



When ready for fertilisation, the archegonium opens. 

 This is due to the pressure of the mucilaginous substance 



