THE FLOWER AND THE BEE 



is to compel the bee to pursue a fixed path to the nectar so that 

 polHnation may be effected with greater certainty. Finally 

 they are more often blue than any other color. So dependent 

 are many flowers upon the visits of bees that, in their absence, 

 they fail to produce seed. Such are the red clover, salvia, lark- 

 spur, and some orchids. 



Irregular or one-sided bee-flowers occur in large numbers in 

 the violet, pea, mint, and figwort families. The nectar is 

 usually not deeper than 7 mm., and the visitors are chiefly 

 honey-bees, bumblebees, and long-tongued solitary bees. 



The species of the violet family consist chiefly of bee-flowers, 

 the general form of which is familiar to every one. One warm, 

 clear day in early May I found the round-leaved yellow violet 

 {Viola rotundifolia) blooming luxuriantly beneath an old beech- 

 tree. Bumblebees, as well as smaller bees belonging to the 

 genera Nomada and Andrena, were flitting busily about from 

 flower to flow^er. On the other hand, our wild blue violets are 

 very sparingly visited by bees or any insects, and are often 

 infertile. (Fig. 20.) This is doubtless the reason why many 

 species produce, besides their showy blossoms, small green 

 flowers (cleistogamy flowers), w^hich never expand but are very 

 fruitful. 



The beautiful and richly variegated varieties of the pansy 

 {Viola tricolor) have been produced partly by selection and 

 partly by hybridization. The corolla may be pure white, 

 yellow, red, blue, purple, or black, or there may be manifold 

 combinations of these hues. (Fig. 21.) These striking diversi- 

 ties result from various mixtures and modifications of two pig- 

 ments contained in the epidermis — violet-colored sap and 

 yellow granules. In the pansy the spur at the base of the 

 lower petal contains the nectar. The anthers lie close together, 

 forming a cone, into the centre of which is shed the dry pollen; 



48 



