130 Practical Plant Biology. 



The archegoniophores are similar to the antheridiophores in 

 their relation to the thallus. They are also differentiated into a 

 stalk and disc ; but the stalk is usually longer and the disc is sub- 

 divided into finger-shaped processes. Like the antheridiophore 

 the archegoniophore is a branch-system, but the growing tips very 

 early turn downwards and inwards towards the top of the stalk, 

 so that their positions are marked by deep indentations in the 

 edge of the disc. The intervening tissues form the radiating 

 finger-shaped processes. The sexual organs, in this case arche- 

 gonia, are formed on the original upper surface of these inturned 

 apices. Owing to the curvature of the latter, the surface bearing 

 the archegonia is turned downwards. The archegonia are formed 

 on a small triangular patch on each branch-tip. This patch is 

 marked out and surrounded by an irregular membrane, which 

 hangs down vertically from it. There are about fifteen archegonia 

 on each patch. Each archegonium is flask-shaped. It has a 

 globular body and a delicate neck. The base of the flask is 

 attached to the patch while its neck hangs vertically downward. 

 The wall of the body of the archegonium is a single layer of cells 

 thick and it encloses a single large spherical cell, the ovum. The 

 neck is composed of six rows of cells surrounding an axial column 

 of cells. The latter soon disintegrates and leaves a passage lead- 

 ing through the neck to the ovum. The archegonia are formed in 

 regular sequence at the growing regions, hence the youngest are 

 found closest to the stalk of the archegoniophore. 



We have seen that it is only when moisture is abundant that 

 the antheridia rupture and expel the sperms ; in the same way it 

 is only when water fills the space enclosed by the membrane sur- 

 rounding the archegonia that the disintegrating column of cells 

 in the neck of the mature archegonium swells up and opens the 

 way up to the ripe ovum. These disintegrating cells give rise 

 probably to some soluble substance which acts chemotactically on 

 the sperms ; for the latter have been observed to crowd round the 

 neck and swim towards its opening. 



The two longitudinal grooves of the stalk of the archegonio- 

 phore are like those of the antheridiophore traversed by bundles 

 of rhizoids which take their origin near the outer end of the 

 finger-shaped rays of the disc. Thus at their base they pass close 

 by the membrane surrounding the archegonia and put this tiny 

 reservoir of water in connection with the water of the soil. The 

 sperms conveyed there by the rhizoids of the antheridiophore 

 may be supposed to find themselves under the orienting influence 

 of the dilute chemotactic substance liberated from the archegonia. 



