1894. HENSLOW AND NATURAL SELECTION. 183 



numerous alleged species, sub-species, and varieties of our native 

 plants. They test the fixity of the characters which distinguish each 

 form by cultivation. If these characters remain unchanged, and are 

 transmitted by seed, the form is a permanent one and deserves to be 

 recorded as a species or sub-species ; but if, as frequently occurs with 

 forms which appear quite as distinct as those which are stable, the 

 plant reverts on cultivation to some other form, it is evidently a 

 modification due to some local conditions of the environment, and 

 should be treated differently. Mr. Beeby has proposed to call the 

 former "intrinsic," the latter "extrinsic " varieties, terms correspond- 

 ing to Weismann's " germ variation " and " somatic variation," and 

 these can in many cases only be distinguished from each other by 

 the test of cultivation under different conditions. On this point Mr. 

 Beeby remarks : — " The most transient states of plants due to the 

 direct action of their environment are often far more distinct in 

 appearance from their normal forms than are some varieties from 

 their types ; but the first-named return at once to their normal state 

 on being removed from their special surroundings, while the latter 

 remain permanently distinct from their types even when grown under 

 circumstances most disadvantageous to the continuation of the par- 

 ticular variation. That these two kinds of variation exist in plants 

 is certain ; and the separation of them seems to be the very basis on 

 which all investigations of the Phanerogamia must be made, if it is 

 hoped that this branch of botany is to throw any further light on 

 Evolution." -^ 



In conclusion, I submit that the whole body of facts in relation 

 to the direct action of the environment indicates that modifications 

 thus produced in the individual are not transmitted to the offspring ; 

 and that until it is demonstrated by experiment that they are so 

 transmitted, theories of plant modification founded on that assumption 

 are altogether worthless. 



Alfred R. Wallace. 



"On the Flora of Shetland." Annals of Scottish Natural History. January, 1892, 

 p. 52. 



