66 



STRUCTURAL BOTANY 



zoid is formed from the nucleus of the mother-cell ; the 

 cilia, however, and the narrow end of the body are 

 derived from the protoplasm. In Fig. 33, B the young 

 spermatozoids are shown enclosed in their mother-cells. 



FIG. 33. Antheridia of Male Fern. A, 1, 2, and 3. antheridia at 

 three successive stages seated on prothallus ; c, central cell ; 

 w, wall. B, older antheridium ; sp, mass of spermatozoid 

 mother-cells ; w, wall. C, a single spermatozoid. Magnified, 

 A and B about 300, C about 700 diameters. (After Kny.) 



In the ripe antheridium every mother-cell contains 

 its spermatozoid curled up inside it; as soon as a 

 drop of water comes into contact with the antheridia, 

 they open, by the bursting of their cap - cells (see 

 Fig. 34). 



The pressure which brings this about is due partly to 

 the swelling of the mother- cells themselves, and partly 

 to that of the ring-cells, which absorb water and press 

 upon the mass of mother-cells, squeezing them out from 

 the antheridium. The whole mass of mother-cells is now set 

 free, but each spermatozoid is still imprisoned within its 

 own mother-cell. The membranes of the latter, how- 



