INSECTS AND FLOWERS 213 



and also the tip of the pistil, is forced out at 

 the top of the keel against the chest and under- 

 surface of the bee. On the departure of the bee, 

 and the consequent removal of the pressure of 

 her body, the keel springs back into place, and 

 the stamens and pistil resume their former posi- 

 tion within the keel. This arrangement may 

 also be seen in the Horse-shoe Vetch, the Lupin, 

 the Rest-harrow (Ononis), and the Bird's-foot 

 Trefoil (Lotous corniculatus). In the case of the 

 last-named plant, it has been ascertained by 

 careful experiment that the process of pumping 

 pollen from a given flower may be repeated 

 eight times. 



The flowers of the White and Yellow Dead- 

 Netties, and of the Salvia, show a remarkable 

 hammer form of mechanism for depositing pollen 

 upon visiting insects. Like so many of our 

 native wild flowers, those of the common White 

 Dead-Nettie are especially adapted for the visits 

 of humble-bees. The petals form a tubular two- 

 lipped corolla, the flower pointing obliquely 

 outwards and upwards from its attachment to 

 the main stem. The curious, curved and arched 

 upper lip protects the pollen and honey from 

 rain, while the broad lower lip forms an admir- 

 able alighting platform for the humble-bees when 

 visiting the flower. The honey-gland or nectary 

 is placed deep down within the tubular corolla, 

 and is further protected from marauding insects 

 incapable of effecting cross-pollination, by a ring 

 of hairs halfway down the interior of the tube, 

 which acts as a kind of rampart against these 

 undesired visitors. The humble-bee in visiting 



