ADAPTATIONS FOK INTERCROSSING. 



need particular mention. One of them, the Bean-blossom, is 

 well known to botanists ; the other not so. The peculiarity in 

 the common Beau, Phaseolus vulgaris, and its nearest relatives, 

 is that the keel, enclosing the stamens and pistil, is prolonged 



into a narrow snout which is spirally coiled (as in Fig. 444-446) ; 

 that the stigma is oblique on the tip of the style, and the beard 

 on the style is mainly on the same side that the stigma is : the 

 wing-petals stand forward and turn downward, forming a con- 

 venient landing place for bees. As in the Locust-blossom, the 

 anthers earl}* discharge their pollen, much of which adheres 



448 



lightly to the beard of the style. In the untouched flower, all 

 from first to last is concealed in the coiled keel. Press down the 

 wing-petals, and first the stigma and then the pollen-laden tip 

 of the style projects from the orifice : remove the pressure, and 

 they withdraw within. When this pressure is made by a bee, 

 resting on the wing-petals while searching for nectar within the 

 base of the blossom between the keel and the standard, the same 

 movement occurs : the stigma first, and then the pollen on the 

 style, strikes against a certain portion of the front or side of 

 the bee's body, and the repetition of this operation causes the 

 fertilization of each blossom by other than its own pollen. A 

 slighter pressure or lighter movement of the wing-petals suffices 



FIG. 444. Flower of Garden Bean, Phaseolus vulgaris. 445 Same with wing- 

 petals pressed down and tip of style projecting from the orifice of the keel. 446. Same 

 as 444 enlarged, and standard and wings removed. 447. Upper part of keel, in the 

 condition of 445, enlarged, showing plainly the projecting style. 448 Section of the 

 keel, enlarged, showing the style within before the anthers open: stamens for sake of 

 clearness not delineated. 449. Pistil detached from an older flower; the brush loaded 

 with pollen. 



