Problems of genetics / by William Bateson.

  • Bateson, William, 1861-1926.
Date:
1913
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Problems of genetics / by William Bateson. Source: Wellcome Collection.

    127/290 (page 105)
    THE MUTATION THEORY 105 some which in botanic gardens pass for original species. Whether actual wild plants from their native habitats are in the same state, is not yet known, but it is by no means improbable. The case may be compared with that of the moth Abraxas grossu- lariata studied by Doncaster and Raynor, in which the females are all heterozygous, or we may almost say hybrids of grossu- lariata and the variety lacticolor. Similarly we may say that at least garden Petunias are heterozygous in respect of singleness. The proof of this is of course that when fertilised with the pollen of doubles they throw a mixture of doubles and singles. The statements which de Vries has published regarding the behaviour of several of the Oenotheras go far to show that they must have a somewhat similar organisation. On the present evidence it is still quite impossible to construct a coherent scheme which will represent all the phenomena in their interrelations, and among the facts are several which, as will appear, seem mutually incom¬ patible. The first indication that the Oenotheras may have either mixed ovules or mixed pollen appears in the fact that Lamarckiana and several of its mutants used as males, with several other forms as females, give a mixed offspring. For example, de Vries (1907) found that biennis 9 X Lamarckiana cf biennis cruciata 9 X Lamarckiana cf muricata 9 X Lamarckiana cf biennis 9 X rubrinervis cf biennis cruciata 9 X rubrinervis c? all give a mixture of two distinct types which he names laeta and velutina, consisting of about equal numbers of each. On account of the fact that the two forms are produced in association de Vries has called these forms twin hybrids, a designation which is not fortunate, seeing that it is impossible to imagine that any kind of twinning is concerned in their production. The distinction between these two seems to be considerable, laeta having leaves broader, bright green in colour, and flat, with pollen scanty, while velutina has leaves narrower, grayish green, more hairy, and furrow-shaped, with pollen abundant. We next meet the remarkable fact that these two forms,