Genetical studies on aenothera / Bradley moore Davis.

  • Davis, Bradley Moore.
Date:
1913
Catalogue details

Licence: In copyright

Credit: Genetical studies on aenothera / Bradley moore Davis. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    19/30 (page 565)
    I am perfectly willing to admit the complexity of my stock material of grandiflora and biennis, and also the possibility that the forms may not have been strictly homozygous at the time the crosses were made. It was in no wise necessary for the purposes of my experi- ments that they should be strictly homozygous. My only concern was that the material should he American types of CEnothera without the possibility of contamination through crosses with Lamarckiana. That my forms of biennis and grandiflora had these qualifications there can, I think, be no doubt. They have, as a matter of fact, bred true in the small cultures which have been carried through two generations for biennis A and biennis D and four generations for grandiflora B. An abstract of my argument is as follows: (1) Since hybrids of biennis and grandiflora show points of strong resemblance to Lamarckiana and, (2) since the behavior of these hybrids in the F2 and F3 parallel closely the be- havior of Lamarckiana when it gives rise to “mutants,” (3) therefore, there are strong reasons for believing that the “mutations” of Lamarckiana are due to instability of its germinal constitution resulting from a hybrid origin. The fact that CEnothera Lamarckiana is not known as a component of any native CEnothera flora and the fact that its known history has been entirely as a cultivated plant or as a garden escape naturally greatly strengthen the force of the above argument. It does not seem to me that these arguments are answered by a supposition that the behavior of my hy- brids involves a habit of mutation inherited from the parental types. On the contrary, are we not justified in asking of the mutationists evidence from material the status of which, as representative of a wild species, is beyond question? Stomps (’12b) has apparently en- deavored to meet the situation by a study of a cross be- tween the biennis and cruciata of the sand dunes of Hol- land. From the cross he obtained in the second genera- tion a biennis nanella and a biennis semi-gigas. Both of