200 SECTIONAL ADDRESSES. 



It is when we come to the work of Turesson in Sweden, and the experi- 

 ments conducted by Clements and by Hall in America, that the importance 

 of transplant work to Taxonomists, Geneticists and Ecologists can be fully 

 understood. Turesson's experiments' have been conducted with great care, 

 and are of far greater value than any previous transplant work. He 

 collected wild material from habitats studied by himself in Scandinavia 

 and other parts of Europe, and worked with a large number of common, 

 widely distributed and ' polymorphic ' species. He has been able to prove 

 that considerable hereditary potential variation exists within these species, 

 and has shown that the naturally occurring variations can be grouped 

 into different types confined to definite habitats. Turesson's experiments 

 indicate clearly that there may be a close parallelism between mere 

 phenotypic modifications (fluctuations of some) and heritable variation. 

 It is only by experiment, however, that a decision can be reached as to 

 whether a given variation has a gene basis or not ; for it is only when its 

 genetical nature is known that the admission of any variation as a distinct 

 species or variety should be entertained from the Taxonomic point of view. 



It is because Turesson has used so large a number of plants of each 

 species in his experiments, that his contributions to the subject of ' race 

 ecology,' or ' gene-ecology ' as he terms it, are of so much value. As far 

 as methods are concerned he has placed this line of work on a sound basis. 

 As to his nomenclature, however, there may be some divisions of opinion 

 into which I need not enter, as it is a matter which mainly concerns the 

 experimental ecologist. 



The value of Turesson's work, speaking generally, may be said to be 

 that he has been able to come to conclusions as to the different types of 

 variation shown by the plant he has observed, both growing wild and under 

 cultivation, and has been able to demonstrate that in some cases they are 

 of a heritable nature, while in others they are merely fluctuations. 



The species problem, therefore, in the light of Turesson's experiments, 

 which are borne out by what I shall have to say about our own transplant 

 experiments, is definitely becoming an ecologico-genetical problem. 



These new lines of research, which bring together Ecology, Genetics 

 and Taxonomy, and are yielding results of value to botanists working on 

 these three lines, are now being actively pursued at Potterne, in Wiltshire, 

 and at Kew along somewhat different lines. 



As I consider them likely to lead to results of considerable importance, 

 I think it will be useful to give a short account of the experiments now in 

 progress. During a visit to the United States, in connection with the 

 International Congress of Plant Sciences at Ithaca in 1926, the transplant 

 experiments that were being undertaken by Prof. H. M. Hall in California 

 were studied. These are being carried out with cloned plants of several 

 genera, and at different altitudes like those of Gaston Bonnier, and it seemed 

 desirable to attempt experiments on somewhat similar lines in England. 

 As, however, experimental cultivation at different altitudes in the British 

 Isles would not be likely to afford results of any great value, it was decided 

 by the Committee appointed by the Ecological Society, who were keenly 

 interested in the proposal, to carry out experiments in growing certain 



' See papers in ' Hereditas,' from vol. iii. 1922, onwards. 



