Volume 6

Opera e periodicis collata.

  • Vries, Hugo de, 1848-1935.
Date:
1918-1927
Catalogue details

Licence: In copyright

Credit: Opera e periodicis collata. Source: Wellcome Collection.

    608/630 (page 580)
    the hybrid might inherit this impurity and show phenomena which might easily be mistaken for mutations. It so happens that 0. biennis is in a condition of mutability analogous to that of 0. Lamarckiana, although not developed to the same high degree. From time to time it produces dwarfs, which are distinguished from it by exactly the same two characters which differentiate the dwarfs of 0. Lamarckiana from their mother species, namely, low stature and sensitiveness to the attacks of some species of soil bacteria.1) Moreover, Stomps has shown that 0• biennis may, although very rarely, double the number of chromo- somes in its sexual cells, which in 0. Lamarckiana produces the two mutants 0. gigas and 0. semigigas.2) As is now generally admitted, 0. gigas results from the pairing of two mutated sexual cells, each of which had a double number of chromosomes. 0. semigigas, on the other hand, is produced by the pairing of a sexual cell mutated in the same way, with a normal gamete; therefore it possesses only 21 chromosomes (14 -f- 7), while the number in 0. gigas is 28. As yet, only semigigas mutants have been observed coming from 0. biennis, and it is obvious that the double com- bination must be much rarer. As a proof of this special kind of mutability in 0. biennis, however, the observations of Stomps are wholly sufficiënt. In quoting these facts, Davis says that if it can be shown “that tested strains of this biennis are able to produce new forms of specific rank or even marked varieties, the mutationists would have much stronger evidence in support of the mutation theory than that based on the behavior of 0. Lamarckiana.”3) After conceding this strong position to his adversaries, Davis subjects the results of Stomps to a rather sharp criticism, which, unfortunately, is based upon a confusion of two wholly distinct types, namely, 0. biennis L. var. cruciata4) and O. cruciata Nutt. He says: “It should be made clear that the form (0. biennis cruciata) is recognized in the more recent taxonomie treatments as a true species sharply distinguished 1) Stomps, Th. J., Mutation bei Oenothera biennis L. Biol. Centralbl. 32:521—535, 1912; also Zeylstra, H. H., Oenothera nanella De Vries, eine krankhafte Pflanzenart. Biol. Centralbl. 31 : 129—138, 1911. Vergl. ferner: Gruppenweise Artbildung 1913 : 296—304. 2) Stomps, Th. J., op. cit. p. 533. 3) Davis, B. M., Mutations in Oenothera biennis L.? Amer. Nat. 47.116 12 i (especially p. 116), 1913; see also op. cit. 47 : 540—596. (especially p. 567), 1913. 4) Die Mutationstheorie 2:599, I9°3-