100 



POLLINATION AND FERTILIZATION 



The Male Gametophyte. — A body of this kind, proceeding from the 

 germination of a matured spore, is properly to be regarded, Hke its 

 female homologue, as a plant body. It is to be noted, in passing, that 

 it can be equally well produced by germination upon other surfaces 

 which present the proper conditions. 



Fig. 277. Diagram illustrating structure of ovule: s, synergidae; u, oGsphere; sek, nucleus; e, 

 embryo-sac; g, antipodal cells. 278. Diagram illustrating fertilization: a, pollen-grains on stigma; 

 6, pollen-tubes penetrating stigma and style and entering ovarian cavity, one of them entering the 

 foramen of the ovule at c. 



Following the same course of reasoning as in the case of the female 

 gametophyte, we see that this pollen-tube is the male gametophyte. 

 Its structure is not, or apparently not, even so highly developed as in 

 the case of the other. 



The Male Cell. — At its lower end are one or more little bodies which 

 constitute the male element and which are to fertilize the oosphere 

 which we have already observed within the embryo-sac. This fertil- 

 izing element is the Male Cell, or Antherozoid. 



In some of the lowest of the flowering plants, and in most of the 

 Cryptogams, this male cell is highly organized, with a specially formed 

 body, is capable of locomotion, and possesses peculiar powers of 

 nutrition. It is comparable with the spermatozoon of animals. 



The Descent of the Pollen-tube. — The male cell or antherozoid is quite 

 as incapable of reproducing by itself as is the oosphere, and its sole 

 function is to act upon the latter, fecundating it. This is accomplished 



