CX.AS3 DIADELPHIA. 157 



character of dividing themselves into 2 equal setts. 

 The calyx is also bilabiate ; the lornent compressed, 

 having one of its sutures straight and the other lobed ; 

 the joints truncated, and each 1-seeded. 



The Kidney-bean (Phaseolus) has the keel of the 

 corolla with the stamens and style spirally twisted. 

 The legume is likewise compressed and falcate, 

 with the seeds consequently somewhat flattened, and 

 reniform or kidney-shaped. By the first and most 

 important of these generic characters you will readily 

 perceive a difference betwixt the flowers of this ge- 

 nus, as in the Scarlet-runner (P. multiflorus), for ex- 

 ample, and the Lima-bean, with others now cultivated, 

 which belong to the genus Dolichos, where none of 

 this twisting of the stamens and keel is to be found ; 

 and, in addition, 2 callosities at the base of the vexil- 

 lum compressing the sides of the keel. We have, 

 however, another genus almost intermediate between 

 these two, and which, in turn, has been referred to 

 both ; but it appears to constitute a distinct genus, now 

 termed Strophostyles, in reference to the twisted 

 character of the keel and its included organs, a char- 

 acter possessed in common with Phaseolus, but the 

 legume is cylindric, as well as the seeds, which are, 

 nevertheless, portly reniform. This little kindred tribe 

 are all trifoliate plants, with showy flowers, and weak, 

 twining, or prostrate stems. Many of their seeds 

 and unripe legumes form important articles of diet, 

 and continue longer in season than any other pulse. 



In shady thickets, and on river banks, where the 

 soil is black and fertile, may often be found another 

 twining plant of free growth, peculiar to the United 

 States, and forming of itself a particular genus, called 

 Apios. Its roots are strings of oblong cylindric 

 tubers, called, sometimes, Pig-potatoes, and Indian 

 potatoes, as when roasted or boiled they have partly 

 14 J 



