SPERMATOPIIYTES : ANGIOSPERMS 



367 



simple, being developed entirely within the spores which 

 produce them. 



The male gametophyte is represented by a few cells which 

 appear within the pollen grain, two of which are male cells. 



When pollination 

 occurs, and the pollen 

 has been transferred 

 from the pollen-sacs to 

 the stigma, it is de- 

 tained by the minute 

 papilla3 of the stig- 

 matic surface, which 

 also excretes a sweet- 

 ish sticky fluid. This 

 fluid is a nutrient so- 

 lution for the micro- 

 spores, which begin to 

 put out their tubes. A 

 13ollen-t.ube penetrates 

 through the stigmatic 

 surface, enters among 

 the tissues of the style, 

 which is sometimes 

 very long, slowly or 

 rapidly traverses the 

 length of the style sup- 

 plied with food by its 

 cells but not penetrat- 

 ing them, enters the 

 cavity of the ovary, 

 passes througli the 

 micropyle of an ovule, 

 penetrates the tissues 

 of the nucellus (if any), 

 and finally reaches and pierces the wall of the embryo-sac, 

 within which is the egg awaiting fertilization (Fig. 327). 



Fig. 327. Diasrram of a longitudinal section through 

 a carpel, to illustrate fertilization with all parts 

 in place : .«. stigma ; g, style ; o. ovary ; ai, ii, 

 outer and inner integuments ; n, base of nucel- 

 lus ; /. funiculus ; b, antipodal cells ; c, endo- 

 sperm nucleus ; k. egg and one synergid ; p, pol- 

 len-tube, having grown from stigma and passed 

 through the microjjylo (»i) to the egg.— After 



LUEUSSEN. 



