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The Coefficient of Mutation in Oenothera biennis L.

1915; University of Chicago Press; Volume: 59; Issue: 3 Linguagem: Inglês

10.1086/331526

1940-1205

Hugo DeVries,

Turfgrass Adaptation and Management

1. In a culture of 8500 specimens of pure line Oenothera biennis L., 8 mut. nanella, 4 mut. semigigas, and 27 mut. sulfurea arose, giving the percentages of about 0.1 per cent, 0.05 per cent, and 0.3 per cent. In cultures of O. Lamarckiana the corresponding numbers are for O. nanella 1-2 per cent, for O. semigigas 0.3 per cent (Gruppenweise Artbildung. p. 329), while no color mutations have been observed as yet. With the origin of O. Lamarckiana the mutability for dwarfs, therefore, must have increased at least tenfold, and for gigas types about sixfold. The material cause for this improvement is in all probability the same as or closely connected with the cause of the largely increased number of mutative forms which are known to start from O. Lamarckiana. 2. From the cross O. biennis mut. nanella x O, biennis only dwarfs of a uniform type arose 108 Ex). O. biennis x O, biennis mut. nanella was in the first generation exactly like pure biennis; O. Lamarckiana x O. biennis mut. nanella exactly like O. Lamarckiana x biennis. O. biennis semigigas is self-sterile, but when pollinated by O. biennis gives for one-half pure biennis with 14 chromosomes, and for the other half a new, slender type with 15 chromosomes. Identical, strictly analogous to those which differentiate the wild species of the whole group. In some cases the differences are even larger. Those between the wild species are often very small and limited to certain life periods, leaving the species quite alike during the remainder of their development. No arguments have as yet been adduced to doubt the fundamental identity of the two groups of characters. 6. The phenomenon of mutability, observed in O. Lamarckiana, O. biennis, and allied forms, is therefore to be considered as a simple continuance of the supposed mutability which presided at the origin of the wild species of the evening primroses. 7. The seeds of the evening primroses are often very slow in germinating, leaving sometimes one half or more of the healthy germs in a dormant condition. This difficulty in the study of mutation percentages, etc., may be overcome by pressing the water into them. A pressure of 6-8 atmospheres during 1-3 days is ordinarily sufficient to stimulate all or almost all the good germs to a rapid germination.