1532 A TEXTBOOK OF THEORETICAL BOTANY 



A further variation of legume structure is seen in the spirally wound 

 legumes which are familiar in Medicago, different species of which show 

 all variants between one partial turn and several complete turns of the 



Fig. 1394. — Arachis Iiypoi^aea. Ground Nut. 

 One of the subterranean legumes opened 

 to show the two seeds. One cotyledon of 

 the upper seed has been removed to show 

 the embryonic plantlet. The point of 

 attachment of the fruit is below. 



spiral. In M. arabica the margins of the fruit are furnished with long 

 spines, pointing in different directions, which form an adhesion mechanism 

 aiding dispersal by animals. Prosopis pubescetis, the Screw Bean of the 

 southern United States, has fruits wound into a long, tight spiral of many 

 turns. The pod is fleshy and is eaten by animals which distribute the 

 seeds in their excreta, as is the case with many other legume fruits. 



(b) Syncarpoiis Fruits. The product of two or more concrescent 

 carpels. 



