22 



LIVING PLANTS 



Pollination 



Organization 

 of shoot 



result of the relations of the organ to the ho- 

 rizon in response to its heliotropism and ther- 

 motropism, it has also acquired in some in- 

 stances a trace of geotropism. The elimina- 

 tion of all but nutritive functions from the 

 leaves has made it possible for these organs 

 to perform such functions with greater eco- 

 nomy, and made superfluous also the pres- 

 ence of any other forms of irritability which 

 would direct the position of the leaf. 



In the accomplishment of the reproductive 

 process, an incidental condition is the trans- 

 ferance of the pollen from its place of forma- 

 tion to the surface of the stigma in the same 

 or other flowers. In a great majority of in- 

 stances the relation of the line adjoining the 

 anther and the stigma to the vertical or hori- 

 zon, is of the utmost importance, whether 

 the pollination is accomplished automatically, 

 by air currents, or by insects, and a well 

 marked geo tropic reaction is therefore gen- 

 erally exhibited by flowers with the motor 

 zone located in the peduncle. These organs 

 also show minor heliotropic reactions. 



The same process of analysis may be 

 applied to the entire shoot, with the general 

 result that each organ will be found to re- 

 spond to a number of forces generally limited 

 to two or three, though of course, instances 

 are not lacking where a greater number of 



