THE FLOWER AND THE BEE 



many irregular white flowers, which have been derived from 

 yellow, red, and blue forms, partly as the result of retrogression, 

 and partly because of the advantage arising from a contrast of 

 colors between closely allied species blooming at the same time. 

 There is a white variety of the scarlet runner, and the bright- 

 blue larkspur is sometimes white. Both white and pink flowers 

 have been seen on a single plant of the snapdragon, and a 

 pure-white form of the bright-red Polygala is sometimes found, 

 and also of the violet-blue pickerel-weed. Everywhere there 

 is ample evidence that a flower containing pigments may easily 

 change to white. 



Finally there are many small white flowers which are soli- 

 tary, or at least not densely clustered. Some 56 such species 

 belong to the pink family; they are low-tufted, weak herbs of 

 a spreading or ascending habit represented by the duckweeds 

 and sandworts. They are visited chiefly by flies and the smaller 

 bees. 



Individual white flowers may develop bright coloration dur- 

 ing their period of blooming. The white sepals of the Christ- 

 mas rose (Helleborus niger) regularly change to green; the 

 flowers of a species of lantana are at first white, but later be- 

 come yellow; while the corolla of the sweet-william, common 

 pink, and Hibiscus mutabilis turn from white to red. In the 

 bellflower (Campanula) the flowers remain white until they ex- 

 pand, when they change to blue. Thus under suitable condi- 

 tions there may come from white flowers a great variety of 

 colored ones. But, as has been already pointed out, white 

 flowers are most common in primitive families in which yellow 

 flowers are also very abundant. 



<2U 



