48 



like Erythrina, are adapted to humming birds. 



Phaseolus vulgaris L/. The common bean is abund- 

 antly self-pollinated, it lias interesting adaptations for secur- 

 ing cross-pollination. The flower of the bean consists of the 

 green calyx and the corolla, which is made up of five parts, 

 the upper part called the standard, two laleral wings, and a 

 keel made uj) of two petals. The keel is spirally coiled and 

 contains the stamens and pistil. The oblique stigma is on 



PIG. 21. 

 Fig. 21 Common bean (P/iaseniuB tmlcraris). 414. the flower. 146. showing spi- 

 rally coiled keel. 448, part of keel remov<>cl, showing style 447, the figure to 

 the right showing style and pollen only. (After Gray) 



the tip on the style, which is bearded, near the end on which 

 the pollen is discharged. An insect in searching for the 

 nectar at the base of the flower lights on the two lateral 

 petals, coming flrst in contact with the stigma, deposits pol- 

 len from another flower. The weight of the insect causes 

 the style to protrude. In scarlet runner {Phaseolus mul- 

 tiflorus) the arrangement is similar except that the keel 

 with its style is so bent that when pressed down, the style 



