ASPIDIUM YOUNG SPOROPHYTE 177 



it will be seen to consist essentially of an outer wall one 

 layer of cells in thickness : this incloses a central mass of 

 cells, the contents of which may be seen to be rounded off, and 

 to have assumed the form of a closely coiled spiral : these are 

 the spermatocytes or mother-cells of the spermatozoids. 



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

 tozoids, 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 archegonium ; 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 finallv coalesce with the ovum. 



C.THE YOUNG SPOROPHYTE, OR FERN-PLANT. 



I. The result of the process of fertilization of the ovum by 

 the spermatozoids is the development of a riew 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 a close 



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