2-6 



FLAX r LIFE. 



Heterogamy. 



Heterogamy is that mode of sexual union in wliich the sex 

 cells are unlike, Ijeing differentiated into sperms and eggs. 



380. The sperms. — The bod}- of the s|)erm is the cell 

 nucleus, surrounded bv a small amoiuit of protoplasm which is 

 often extended into one or more cilia (fig. 306). The more 

 complete the differentiation of the sperm the smaller, as a 

 rule, is the amount of body ijrotofjlasm. Whether or not the 

 sperm is motile depends upon the conditions to which it has 

 become adapted. Whenever motile, fertilization must occur 

 in the presence of water of amount sufficient to permit the 

 sperm to swim lo the egg. 



Fig. 306. — .Sperms of various plants, showing variety of form, t, I'oItox aureus; 

 2, I'auchi'rin syjhiihh-a : 3, Ck,ira J'rngUis : ^, J'ul-us ^crr,it us : 5. Mar,-/ni?!lia 

 f'o/ymorA/ia : (i, h'q ,i isetum Tehuntcia : 7, Marsilio 7u-slita. Magnified 1000 

 diam. — After Moljins 



The spermary may produce only one sjierm (fig. 307), or 

 its contents may divide into many (fig. 310). Wlien single. 



