ASPIDIUM YOUNG SPOROPHYTE 317 



The dehiscence of the antheridia, the escape of the spermato- 

 zoids, and their movement, should be observed with particular 

 attention in fresh prothalli mounted in water ; also the opening of 

 the apex of the neck of the archegonia ; in both cases the process 

 depends upon a mucilaginous degeneration of cell-walls of the 

 inner cells, and a subsequent swelling by taking up water, and 

 consequent rupture of the outer walls. Further, the movements 

 of the living spermatozoids may be followed, and the act of 

 fertilization observed : the spermatozoids pass through the mass 

 of mucilage which fills the neck of the archegonium, and finally 

 coalesce with the ovum. 



C.THE YOUNG SPOROPHYTE, OR FERN-PLANT. 



I. The result of the process of fertilization of the 

 ovum of the archegonium by the spermatozoids is 

 the development of a new Fern-plant (the sporophyte), 

 and in cultures which have been continued for some 

 months such young Fern-plants may be clearly seen 

 attached to the prothalli, but one prothallus produces 

 only one young Fern-plant. 



Select a prothallus to which a young Fern-plant is 

 thus attached, and wash from it the soil which adheres 

 to it. Examine it with a lens, and observe 



1. That the prothallus itself is similar in form and 

 structure to those before observed. 



2. That the young Fern-plant is firmly attached to 

 its under surface by a lateral protrusion (foot). 



3. That the young Fern-plant consists of the following 

 parts : 



a. A root, which turns downward into the soil. 



b. A lateral protrusion, the foot, which maintains 



