THE PROBABLE ORIGIN OF OENOTHERA 

 LAMARCKIANA SER. 



(With Plates I -111.) 



In a series of most interesting articles B. M. Davis has recently 

 tried to prove that mutability might be a result of previous crosses. 

 This view was first proposed by Bateson and Saunders, and applies 

 especially to the phenomena which Oenothera Lamarckiana shows 

 when seeds from the pure strain, and even from pure lines within 

 this strain, are sown, as in the experiments I conducted in my 

 experimental garden. Davis expected to be able to offer the desired 

 proof by showing that 0. Lamarckiana might be duplicated by 

 crossing two other species of the same group. Up to this time, 

 as a matter of fact, he has not succeeded in producing any form 

 which comes sufficiently near 0. Lamarckiana to be compared with 

 it.i) But if he had succeeded in doing so, evidently it would not 

 have been a proof for his assertion, unless his hybrid should show 

 the same degree of mutability as does 0. Lamarckiana, since we 

 have as yet no means of judging from the morphological characters 

 of a given plant whether its hereditary characters are in a stable 

 or in an unstable condition. 



In starting his experiments to produce a duplication of Lamarck's 

 evening primose, Davis was unfortunate in the choice of the species 

 for his combination. He chose 0. biennis L. and a form which he 

 assumed to be 0. grandiflora Alton. It is evident that the first 

 condition of success in such work consists in the purity and the 

 immutability of the species which are to produce the hybrid. If 

 they are already in a mutable condition, it is to be expected that 

 their hybrids, or at least some of them, may combine the different 

 lines of mutability of their parents; and at all events, the muta- 

 bility of such a hybrid would be no proof that this phenomenon 

 may be produced by means of crossing. On the other hand, if the 

 species to be crossed, or even only one of them, were not pure. 



i) For a successful duplication of an elementary species by means of 

 crossing, see Oenothera biennis X O. cruciata Nutt. in Oruppenweise Art- 

 bildung, p. 311. 



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