Ainpliicarpcsa ino7ioica. 29 



which are destined to produce indurated tissue ; other factors 

 suppress any such tendency. Yet it has been shown that 

 some intrinsic properties firmly hold their own, provided the 

 special legume is allowed to attain a sufficient degree of develop- 

 ment in a definite natural environment, before being subjected 

 to a new one. 



We are thus able to trace gradual transitions in the structure 

 of the flowers of the legumes and of the seeds, while we are like- 

 wise able to prove experimentally what external agents greatly 

 modify the results in various cases. It is evident, therefore, that 

 the subterranean seed habit must have originated in response 

 to some extrinsic conditions, and our observation of the plant 

 in its native haunts must convince us that the above-named 

 characteristic has now become an inherited one. 



In conclusion I will call attention to another line of inves- 

 tigation which Aviphicarpcca has presented. During the lat- 

 ter part of August, 1897, Professor Macfarlane observed in the 

 neighborhood of Strafford Station on the main Pennsylvania 

 Railroad (about twenty miles from Philadelphia), a number of 

 plants which bore white flowers. He mentioned the fact to 

 me, and some time later I visited the spot. The plants were 

 then in fruit. Those legumes which resulted from the evident 

 flowers (in this instance — white) were almost invariably four- 

 seeded. The plants bore many of these, and likewise others 

 which, from position and shape, I knew to be the product of 

 green aerial flowers ; these were almost invariably three-seeded. 

 The plants extended along the roadsides and in the woods 

 for about a mile. 



After noting the above facts, I examined again very carefully 

 the number of seeds in the legumes of the purple-flowered 

 Amphicarpcsa, and found that as a rule those legumes pro- 

 duced by the colored flowers contained three seeds, but those 

 from the cleistogamic only two. The underground legumes 

 of the Strafford variety are small, and pale in color ; many 

 are nearly pure white. As the character of the soil was not 



