THE FOKMS OF FLOrvAL ORGANS. 



107 



a 6 



Fig. 31. — Duveriioia adhatoduulcs. 



come into existence ? And no answer is forthcoming. ITow 

 turning to Fig. 31, h, we see one use at least. The weight of 

 the bee must be very 

 great ; and the curious 

 shape of the lip, with 

 its lateral ridges, is evi- 

 dently not only an ex- 

 cellent landing-place, 

 but is so constructed 

 as to bear that weiarht. 

 Moreover, the two 

 walls slope off, and are 

 gripped by the legs of 

 the bee, so that it evidently can secure an excellent purchase 

 and can thus rifle the flower of its treasures at its ease. 



Irregular corollas are very numerous, but certain prin- 

 ciples, traceable to insect action, govern their forms. In the 

 first place, the side upon which the insect rests, or at least 

 upon which its weight is thrown, is always enlarged, and 

 mostly forms the landing-place. It is almost always the 

 antei'ior petal; if, however, the pedicel or ovary has been 

 too slender to support it, then it has sometimes become 

 twisted, and the flower is said to be resupinate, so that the 

 posterior petal becomes anterior in position, and is now the 

 larger one, since it supplies the landing-place for insects, as 

 in Orchis. Fumaria might be called semi-resupinate, as the 

 corolla has only rotated through 90°. A slight modification 

 occurs in the "Bee-orchis," Oplirys apifera, which is usually 

 described as having a twisted ovary like a true Orchis ; but in 

 this species it has scarcely if any twist at all ; the flower, 

 however, is bent over to the opposite side of the stem, so that 

 while the posterior petal is still the labellum, the ovary has 

 itself remained perfectly straight. 



