272 Schively — Contributions to the Life History of 



General Conditions of Life. 



Amphicarpcea monoica is a plant quite widely distributed 

 throughout the eastern United States. It is, indeed, one 

 of our most common weeds. Its favorite habitat is the 

 woods, where its fresh, green foliage presents an attractive 

 appearance during the spring and summer. It seems to 

 grow more luxuriantly, if it obtains a considerable amount 

 of sunlight, and if the roots receive abundant moisture. 

 Continued exposure to the sun's rays has an injurious 

 effect upon the delicate leaves. It thrives best in a rich 

 loam, but vigorous plants grow in clay or gravel, provided 

 the water supply is fairly plentiful. 



The roots are fibrous and copiously branched. Upon 

 these occur singly or in clusters, the tubercles that are char- 

 acteristic of the Iyeguminosse. They are nearly spherical, 

 but slightly flattened, varying in diameter from one to five 

 millimeters. They are found when the plant is but a few 

 inches high. The number varies according to the char- 

 acter of soil, and whether the plant is grown in a pot or in 

 the open. (Plate XIX.) The comparative production of the 

 tubercles in different soils has not been studied experi- 

 mentally ; but they seem to be more numerous, as well as 

 larger, if the plant is grown in a pot. 



Wood, Gray, and other botanists refer to A. monoica as 

 "perennial." In this latitude there is no evidence of this 

 being typically the case. The plants appear in the spring 

 as the result of the germination of the seed. A very few 

 instances which indicate variation from this rule have been 

 found. While gathering underground seeds in the autumn 

 of '95 I collected a plant possessing long thickened roots, 

 which could be described as tuberous. Unfortunately the 

 fact was not noticed, until too late to ascertain whether the 

 plant would really have perennated or not. In the spring 

 of '96, several specimens were obtained, in which, from 

 thickened root and lower stem region, arose the new plant ; 

 at one side persisted the dried remains of last year's stem. 

 (Plate XXXIL, Fig. 1.) 



