FERTILIZATION. 161 



the time of the expansion of the flower, the rfvules are gene- 

 rally fully formed and ready to receive the impregnating influ- 

 ence of the pollen. They have become regularly shaped 

 usually roundish bodies fixed to the placenta by one side. 

 They are not yet seeds, but are destined to become seeds at a, 

 future period. 



CHAPTER XIII. 



THE PROCESS OF FERTILIZATION OR FECUNDATION. 



Functions of the stamens and pistils. — Fecundation is that 

 function by which the pollen is brought into contact with the 

 pistil, so as to produce within the ovule the formation of an 

 embryo. The results of fecundation are the transformation of 

 the ovules into seeds and of the carpels into fruits. Let us 

 consider, — 



1. The preparatory or precursory phenomena of fecundation, 

 or the arrangements made for securing the application of the 

 pollen to the stigma. Fecundation in general takes place at 

 the period of anthesis, {m9ri<ii,s, flower opening.) The anthers, 

 up to this time unruptured, open their cells, and spread the 

 pollen over the stigma and very frequently over the other 

 parts of the flower, and it is then that fecundation is effected. 



There are however a certain number of plants among which 

 fecundation takes place before the expansion of the floral 

 organs. This is the case with many of the Compositae and 

 Aster tribe which have syngenesious stamens, the stigmas and 

 styles of whose pistils are clothed with what botanists have 



