36 SEX 



grains of ordinary flowering plants, although 

 they correspond to the whole male generation, 

 and usually abbreviate away the formation 

 of spermatozoa in adaptation to the loss of 

 watery environment, are adapted to passive 



Fio. 6. Female reproductive organ or archegonium in the 

 Adder's Tongue Fern Ophioglossum and the motile 

 male cells or antherozooids (SP). The egg-cell is marked 

 V ; it lies in a flask-like recess, the neck of which shows a 

 mucous secretion through which the male cells make 

 their way. (After Bruchmann.) 



transportation, from blossom to blossom, by 

 the wind or by the agency of insects (Fig. 7). 

 To the question why the dimorphism of 

 germ-cells should have been justified in the 

 course of evolution, two answers may be 

 given, (a) A number of facts point to the 

 general conclusion that cross-fertilisation is 

 advantageous. Darwin first clearly showed- 



