28 Schively — Recent Obsei'vations on 



usually necessary to compare many plants or perhaps to 

 undertake a series of experiments, frequently repeated during 

 many years ; even then the data may be neither satisfactory 

 nor convincing to the investigator. A strong and plausible 

 hypothesis may be advanced, but the difficulty is to obtain 

 direct and sure proofs. 



Considering the various types of flower found upon speci- 

 mens o{ AiftphicarpcBa growing in the woods, or upon their 

 borders, the opinion might be advanced that there are distinct 

 species, some of which never produce purple flowers and their 

 legumes. But the experimental evidence is conclusive proof, 

 that one plant is capable of bearing all varieties of flower and 

 fruit. Yet we cannot determine why in its native haunts, 

 Amphicarpcea may produce all three forms of legume, some- 

 times but two, or again but one. 



The formation of the subterranean legumes has become a 

 definite part of the plant's inheritance, and for many reasons 

 may well be regarded as an acquired characteristic rather than 

 as an example of indefinite variation, since it is not usual for 

 plants to bear fruit in this manner. What factors originally 

 operated to cause the production of this type of seed, and to 

 fix the result as a habit, it is impossible to say ; but the trans- 

 mission is now undoubted. Often, indeed, no aerial legumes 

 are formed, and the reproduction of the species is dependent 

 solely upon these subterranean seeds. 



While then the germ-plasm cells transmit the tendency to 

 form legumes, whose morphological and histological features 

 differ so greatly from those of the original type, yet when it is 

 considered with what ease and rapidity either type of legume 

 will respond to changed environmental conditions, the centres 

 of variation seem to reside in the somatoplasm, and gradually 

 affect the reproductive substance. 



Two flowers in the same stage of development may be 

 artificially forced to produce legumes quite different in charac- 

 ter. Certain extrinsic factors stimulate, for example, the cells 



