34 



GEXERAL BIOLOGY 



the physiology of the plant ; it secretes but a little nectar 

 — that little on the outside of the spurs — not enough to run 

 down into the sac where the bee's proboscis can reach it. 

 There is, however, a small bee-fly {Bomhylius major) 



that is able to 

 get the nectar 

 which hangs in 

 minute droplets 

 on the outside of 

 the spurs (fig. 

 26). It is often 

 seen poising be- 

 fore a flower, 

 making an ob- 

 lique thrust at 

 each side of the 

 entrance, push- 

 ing its excessive- 

 ly slender proboscis, not down the proper middle passage- 

 way at all, but between the spur and the wall of the sac. 

 Thuq, it touches neither stigma nor pollen, and gets the 

 nectar without doing the flower any service in return. 



But even if this, our commonest violet, has been deserted 

 by its proper visitors, and left to the comradeship of nectar 

 thieves, if its fine adaptations have become useless and its 

 pretty flowers are left to waste their diminished 'sweetness 

 on the desert air,' the plant has not been without resource: 

 after the showy flowers of spring cease to appear, it devel- 

 ops at the surface of the soil minute self-fertilizing 

 (clistogamous) flowers, which shun the light, never rise up 

 into view and never open, but which are abundantly 

 fertile, and are produced all summer long^ (fig. 27). 



Fig. 26. A beefly {Bombylius major) visiting the violet 

 tlower. 



*These clistogamous flowers will be examined in Study 51. 



