380 GENERAL MORPHOLOGY OF PLANTS 



reduced, consisting of the tube cell and generative cell (central 

 cell), i.e., the mature pollen grain. The stamen is a member of 

 the flower when we are considering the principal parts of the 

 flower structure or form. It possesses certain characters of 

 form, size, structure, etc., which are correlated with its functions 

 of spore production, and since the spore on germination produces 

 the male sexual organs, these characters possessed by the stamen 

 are qualities of maleness. From this point of view the stamen is 

 a male member of the flower. In a similar way the pistil is nat 

 the female sexual organ. It is the female member of the flower 

 and is the organ for the production of the macrospore (or female 

 prothallium) which in turn gives rise to the sexual organ, here 

 reduced to the egg, the wall of its case wanting. 



The following table will serve to indicate these relations. 



Stamen = spore-bearing leaf = male member of flower. 



Anther locule = sporangium. 



Pollen grain = small spore = reduced male prothallium 



and sexual organ, sterile part of prothallium 



not formed. 



Pistil, or carpel = spore-bearing leaf = female member of flower. 

 Ovule = sporangium. 



Embryo sac = large spore = female prothallium containing 



the egg. 

 The egg = a reduced archegonium = the female sexual 



organ. 



544. Life history of the Angiosperms. Since a thorough 

 study has been made of the sporophyte of the Angiosperms in 

 Part I, this account will treat briefly of the gametophytes and the 

 early stage of the embryo, in order to form a basis for comparison 

 with the lower plants. 



545. The male gametophyte. The male gametophyte be- 

 gins with the pollen grain, or microspore, four of which are 

 formed from a mother cell in the anther sac. When the pollen 

 grain is ripe it usually consists of two cells, one the tube cell with 

 a prominent nucleus, the other a smaller cell with no cell wall, 



