34 



GENERAL 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 (Bombylius major) 



that is able to 

 get the nectar 

 which hangs in 

 minute droplets 

 on the outside of 

 the spurs (fig. 



^ 26). It is often 



PlBfc^ W^ seen P oism g be - 



-f~ 1 



making an ob- 

 lique thrust at 

 each side of the 



FIG. 26. A beefly (Bombylius major) visiting the violet entrance, push- 



flower - 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. 

 Thus, 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). 



*The.se clistogamous flowers will be examined in Study 51. 



