KNOWLEDGE OF THE MUTATING OENOTHEEAS. 3 



place can now be assigned to mutation as an evolutionaiy factor. Without anticipating 

 the more minute analysis of the mutation process in Oenothera, I may be permitted to 

 state certain points of view at which I haye arrived. 



One of the facts which I shall be particular to emphasize in this paper is that, 

 although a continuous series can be formed between a mutant and its parent in the 

 case of many characters, yet each of the mutants is actually discontinuous in its origin, 

 its organs exhibiting a decided break from those of the parent. 



If a colony of 0. LamarcTciana and its mutants were growing together in large 

 numbers, any casual observer would probably consider that they represented one general 

 "widely- variable or polymorphic species. Yet experiments show that each type originates 

 discontinuously, and that the diiferences, which are exhibited in every organ, arc as 

 great as are to be seen in elementary species. Some of the forms would very probably 

 be given specific rank by " splitters " if they were collected wild, while the others 

 would certainly rank at least as varieties, or forms. 



It has to be remembered, however, that in cultures the characters arc better displayed 

 and developed than can usually be the case with wild forms under conditions of 

 competition with surrounding vegetation. In this sense, and also through improvement 

 in the conditions of nutrition, cultivation brings out differences which would otherwise 

 escape the observer, but it is probable that there is no other direct effect of cultivation, 

 at least in early years. There is, however, some rather cogent evidence [ef. Hill, 1912) 

 for the view commonly held by horticulturists, that after a period of years, cultivation 



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induces variability. Parwin also believed in the existence of this effect, which he 

 ascribed to *' changed conditions." Definite experimental proof of such an effect is 

 greatly needed. It seems probable that change of climate or of soil might account for 

 all such cases of induced variability, rather than any direct effect (such as increased 

 nutrition or freedom from competition) of cultivation itself. Many such cases are, of 

 course, to be explained by crossing. 



This brings us to a consideration of the status of 0. Lamarckiana. As regards 

 its characters, it is undoubtedly a '*good species," differing throughout from 

 0. grandijlora, O. biennis, and 0. muricata, its nearest relatives. Its mutants 

 are grouped like a constellation of satellites around it, and none of them exhibit any 

 character closely approaching any other known species. Nearly all agree with 

 O. Lamarchiana in certain bud-characters and in pubescence, though they all differ 

 markedly in foliage. As regards the cause of this type of " variability," several reasons 

 might be ascribed : (1) crossing ; (2) change of climate or other effect of cultivation ; 

 (3) internal mutational changes independent of any of these. 



Considering the first of these, it is clear that O. Lamarchiana, like all other open- 

 pollinated plants, must have at one time undergone crossing. This fact has been 

 emphasized in another paper (Gates, 1911 J), and here I need only state that whether 

 0. Lamarchiana originally existed in the wild state as an isolated species or, as seems 

 more probable, was only one of many freely intercrossing races alon^ witli certain forms 

 of 0. (jrandijlora, is immaterial if we admit, as we must, that open-pollinated colonies 



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