ORIGIN OF THE ANTHERIDIA. 



95 



The mode of origin of the mother-cells differs considerably in 

 different ferns, but in all cases is essentially as follows : An ordi- 



FIG. 58. (After Suminski, slightly modified.) Adult prothallium of Pteris serrulata seen 

 from below, showing the rhizoids ir) at the posterior end, the depression at the anterior 

 end; the cushion near the latter bearing (in this case) four archegonia. Amongst the 

 rhizoids are the (spherical) antheridia. The chlorophyll-bodies only are shown in the 

 cells of the broad plate of tissue constituting the prothallium. Just above the anterior 

 depression is seen a prothallium of the natural size. 



FIG. 59. (After Strasburger.) Mature anthe- 

 ridium of Pteris serrulata. p, peripheral 

 cells; JH, mother-cells of the spermato- 

 zoids. 



"-w- 



FIG. 60. Diagram to illustrate the origin 

 of an antheridium. A, very young 

 stage; B, older; o, original epidermal 

 cell enlarged; 6, mother-cell of the en- 

 tire antheridium. 



nary cell on the lower side of the prothallium swells and forms a 

 hemispherical or dome-shaped projection, which is soon separated 



