256 The Ohio Naturalist. [Vol. XIV, No. 4, 



The fluctuation I wish to call attention to is of a somewhat 

 different character and involves morphological peculiarities of 

 form and quality. The common sandbar willow, Salix interior, 

 is typically a rather smooth plant with long linear lanceolate 

 leaves. For several seasons I have had this plant under considera- 

 tion at Cedar Point, Ohio, and last suminer collected a series of 

 forms ranging from the water's edge on the bay side to the dry est 

 sand dunes and blowouts on the lake side. There is a perfect grad- 

 ation from nearly glabrous plants at the water's edge to very 

 white-hairy individuals in the hot dry sand, and from the long 

 linear-lanceolate leaves of the hydrophytic plants to the long oval- 

 lanceolate leaves of the individuals growing in the extreme xero- 

 phj^tic conditions. The latter fomi has been called Salix wheeleri, 

 being regarded by some as a species and by others as a variety. 

 When one compares the two extremes, there is a most striking 

 differences — a much greater difference than exists between a 

 very larger number of recently manufactured species. Now why 

 is there such a gradation from plants growing in one extreme to 

 the other? The final answer cannot be given until breeding 

 experiments are carried on. It might be mentioned that carpellate 

 plants are more abundant in the wet soil while the dry sand plants 

 are nearly all staminate. The observations in the field indicate 

 that the individual responds in its growth to its environment. 

 Either the same hereditary factors can respond so as to produce 

 diverse structures or there are factors latent under one set of con- 

 ditions and active in another. If a complex hereditary constitu- 

 tion is involved it should be possible to segregate at least part of 

 the factors involved and thus establish distinct, pure varieties 

 which would no longer be able to respond in such an extreme 

 manner. But if, as is probable in this case, it is merely the response 

 of factors to a greater or less degree to environmental causes, 

 •during growth, than no such segregation could be brought about. 

 Whether the one or the other extreme could be established as a 

 permanent, hereditary variety would depend on whether it is 

 possible to produce hereditary responses of the same nature as 

 arc shown in the individual response during growth. This is an 

 open question far from being settled at the present time. There 

 is no object in asserting the one or the other hypothesis. But so 

 far we have no direct evidence that the individual response can 

 influence the hereditary constitution thru which it acts. It is 

 important, however, to recognize the reality of the diversity of 

 individual response leading to indivddual adajitation to the en- 

 vironment. Some who have speculated along these lines have 

 evidently not had a very thoro systematic and morphological 

 knowledge of the plants in the field with which they were dealing. 



Date of Publication, February 23, 1914. 



