224 



MORPHOLOGY 



carineae the vegetative cells are numerous (as in podocarps). As in 

 Taxaceae, the generative cell divides into stalk and body cells, and the 

 body cell passes into the pollen tube, where either it divides into two 



Figs. 494-500. — Male gametophyte of Pinus: 494, the forming tetrad of spores 

 (pollen grains) within the mother cell; 495, young pollen grains forming wings; 496, a 

 single mature pollen grain; 497, first vegetative cell cut ofif; 498, second vegetative cell 

 cut oS. (first one disorganizing) ; 499, division to generative cell and tube nucleus (both 

 vegetative cells disorganized) (shedding stage) ; 500, growth of the pollen tube, into which 

 the tube nucleus has descended ; division of generative cell into stalk (upper) and body 

 cells. — After Coulter and Chamberlain. 



cells (male cells), or its nucleus divides into two nuclei (male nuclei). 

 The male cells in Abietineae are generally unequal, a condition appar- 

 ently connected with the fact that only one functions; but in Taxodineae 



