F] 



owers. 



197 



perfectly united at the top, leaving a tube entirely open 



at the apex. The inner surface of this tube is stigmatic. 



The stigmatic tube does not ^■r<"~'~"'~"'~'- 



open directly into the cavities 



of the ovary, but sends off 



three very narrow branches, 



each of which communicates 



with the cavity of a carpel. 



Accordingly, when pollen is 



once deposited on the inner 



surface of the main stigmatic 



tube, the pollen tubes find easy 



access to the ovules in each of 



the three carpels. The pollen 



is sticky and hangs together in 



masses, so that it is not adapted 



to being carried by the wind, 



and it is apparently impossible 



for it to get to the stigmatic tube without some outside 



agent. 



A small amount of nectar is secreted, but it is excreted 

 at the very base of the pistil, so that insects seeking it would 

 be far removed from the stigmas. Indeed, the low position 

 of the nectar would seem rather to lead insects away from 

 the stigmas. The flowers are borne in compound racemes 

 high aloft on a strong woody shaft, and, because of their 

 rather strong odor when new buds are opening in the 

 evening and their white color, they are quite certain to 

 make their presence known to insects flying in the 

 twilight (see Fig. 115). 



If we take these facts as our clew and attentively watch 

 these flowers about eight o'clock in the evening, the method 

 of cross pollination will be made clear. A white moth, 



Fig. 114. 

 Photomicrograph of the leg of a 

 honey bee with a chain of four 

 corpuscula clinging to it. The 

 last two corpuscula are still bear- 

 ing one pollinium each ; the re- 

 maining six pollinia have doubt- 

 less been deposited by the bee in 

 stigmatic chambers. X 5. 



