THE FLOWER AND THE BEE 



is lodged on a receptive part of the stigma, where it soon germi- 

 nates. 



The pea (Fig. 22), bean, clovers, locust, vetch, alfalfa, and a 

 host of leguminous allies, are grouped together in the pea family, 

 or Papilionacece — a name derived from the Greek word for 

 butterfly, because of a fancied resemblance of the flowers to 

 that insect. Most of the 5,000 described species are bee- 

 flowers, although there are a few bird and butterfly flowers, 

 and at least 13 species are known which, in the absence of 

 bees, are infertile. For the most part 9 of the 10 stamens 

 unite to form a tube, at the bottom of which lies the nec- 

 tar, if present. Four of the petals interlock around this 

 tube, while the fifth, called the standard, is broad and erect 

 and brilliantly colored to attract the attention of insects. In 

 order to obtain the nectar, a bee rests upon the two lateral 

 wing-petals, which act as levers, braces its head against the 

 standard, when, if it is strong enough, the keel is depressed, 

 and it may introduce its tongue in an opening at the base of the 

 staminal tube. In this family the pollen is applied to the 

 under-side of a bee's body in four different ways : It may es- 

 cape through a valve, or it may be pumped out, or brushed 

 out, or there may be an explosive mechanism. 



But what if it is not strong enough to depress the keel? 

 Then it does not get the nectar. Notwithstanding their beauti- 

 ful hues and honey-like perfume, the flowers of the sweet pea 

 (Lathyrus odoratus) are very rarely visited by bees. Why is 

 this? So firm is the closure of the flower that only a very 

 powerful bee is able to depress the keel and obtain the nectar. 

 Doubtless in its transatlantic home (for the sweet pea is not 

 endemic in America) there are bees strong enough to push 

 open the flower. During one summer observations continued 

 for several weeks failed to reveal a single visit by any species 



50 



