PHYSIOLOGICAL AND BIOLOGICAL RELATIONS 99 



lished between them. The proteins of the cow-pea and soy-bean, while 

 closely resembling, in many respects, the proteins of the legumes just 

 mentioned, are not exactly the same, while the proteins from different 

 species of Lupinus present common characteristics but differ from the 

 proteins of the other leguminous seeds. The proteins of Lupinus, how- 

 ever, resemble proteins of other leguminous seeds more closely than 

 those found in non-leguminous seeds. The proteins of different species 

 of Juglans appear to be identical so far as they have been examined, 

 but differ in one respect or another from the proteins of other plants. 

 We thus find similar proteins only in seeds which are botanically closely 

 related, and it would seem that these differences in the reserve food 

 substances of the seeds must have an important bearing on the de- 

 velopment of the embryo which derives its first food from them. This 

 food substance, as well as the tissues of the embryo itself, are the final 

 products of the metabolism of the plant which produced them. When 

 the embryo first develops it is supplied with a definite food which for 

 each individual of the same species is the same, but for those of differ- 

 ent species is different. Each member of a species thus begins its 

 individual life under similar chemical conditions, but under chemical 

 conditions which are different from those of every other species. It 

 seems probable, therefore, that when the plant has reached a stage of 

 development at which its organs of assimilation are able to furnish it 

 with nutriment from its external surroundings, its chemical processes 

 have already been established along definite lines which it must follow 

 throughout the rest of its life. 



