106 THE STOKY OF THE PLANTS. 



fertilising pollen. But once it has burst, it re- 

 mains permanently open, the keel hanging down 

 in a woe-begone way, so that no bee troubles 

 himself again to visit it. This saves time for the 

 bees, and enables them quicker to fertilise the 

 remaining flowers ; for when they see a gorse- 

 blossom " sprung " as we call it, they recognise 

 at once that it has already been fertilised, and 

 they know they can get no food by going there. 

 In the lupine, on the other hand, and in the 

 common little English birdsfoot-trefoil, the keel 

 is sharp at the point, and the pollen is shed into 

 it before the flower fully opens. When a bee 

 lights on the knobs at the side, he depresses the 

 1 keel, and the pollen is pumped out against his 

 breast in the most beautiful manner. I hope 

 my readers will try some of these experiments in 

 summer for themselves, and satisfy their own 

 minds whether these things are so. 



So far, we have dealt mainly with flowers in 

 which the petals are all still distinct and 

 separate. But in a great many plants, the petals 

 have grown together, so as to form a single 

 piece, a "tubular corolla," as we call it. This 

 arrangement is very well seen in the harebell, 

 the Canterbury bell, the heath, and the con- 

 volvulus. How did such an arrangement arise ? 

 Well, in many flowers even with distinct petals 

 there is a slight tendency for adjacent parts to 

 adhere at the base ; and in certain blossoms 

 this tendency to adhesion must have benefited 

 the plant, because it would allow the proper 

 fertilising insect to get in with ease, and to find 



