THE FLOWER AND THE BEE 



a bumblebee enters the flower it spreads apart the arched 

 fihiments, opening the pollen receptacle, and covering the 

 thorax with fine grains of pollen. 



Since both methods of lodging the pollen on the body of a bee 

 have proved effective, it may be inquired why have two directly 

 opposite courses been followed in different families. To answer 

 this question it is necessary to go back to an early stage in the 

 history of the pea, mint, and figwort families, when as yet the 

 flowers were wheel-shaped or regular in form. In the ancestral 

 plants from which the pea family was derived the stamens 

 were long and projected far out of the corolla, so that insects 

 alighted on the anthers and filaments, pushing them downward. 

 But in the primitive stock of the mint and figwort families the 

 stamens were short and nearly included in the corolla-tube. 

 When a bee rested on the lower lip its head came beneath the 

 anthers, which were pushed up against the helmet, just the 

 opposite of what happened in the pea family. The pollen was 

 consequently placed on the bee's back. If the anthers stood 

 directly within the entrance to the corolla, as in the violet, 

 then the bee was compelled to run its tongue between them. 

 Thus in the evolution of these families it was the length of the 

 stamens which determined where the pollen should be placed 

 on the insect visitor. 



Regular flowers, like the buttercup and rose, always stand 

 vertical, that is, if erect they face the sky, or if pendulous 

 the e9.rth. Irregular, or bilaterally symmetrical flowers, on 

 the contrary, always stand horizontal, or face the horizon. 

 This is well shown in the dense flower-cluster of the horse-chest- 

 nut, where the lateral flowers are irregular and the single 

 terminal flower rotate or regular. Vertical flowers, like the 

 borage or strawberry, are approached by insects with equal 

 ease from every side, and the forces which might change their 



60 



