File:Plant-breeding; comments on the experiments of Nilsson and Burbank (1907) (14802323303).jpg

Identifier: plantbreedingcom00vrie (find matches)
Title: Plant-breeding; comments on the experiments of Nilsson and Burbank
Year: 1907 (1900s)
Authors: Vries, Hugo de, 1848-1935
Subjects: Burbank, Luther, 1849-1926 Nilsson, Nils Hjalmar, 1856- Plant breeding
Publisher: Chicago, Open Court Pub. Co.
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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s may have been brought aboutby rare sports as well as by long continued changes; theeffect, at the present time, would be the same. Darwinagreed that this possibility could not be denied and that itwas a very weak point in his hypothesis of slow evolution. The mutations must not be assumed to be considerablechanges. From a study of the differences among smallspecies, we may form some conclusion as to their probablesize. Common observation shows the difference betweenclHed species, ordinarily, to be quite striking; but a littlediscussion and a closer inspection will easily prove that, insuch cases, the differences are due to more than one, andoften to numerous, characters. In groups (such as bram-bles, roses, buttercups, willows, and many others), wherelarge numbers of species are closely allied, the differencesbetween any two of them become smaller, and, the numberof cUstinct forms increasing, the distinction, in the end, maybecome reduced to one single differential mark for each two
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Fig. I A. The Oak-leaved Hazelnut (Cor>/H5.4tr//<7»a/acm/a/a), a naturalsport of the ordinary hazelnut (B). 8 PLANT-BREEDING neighboring types. Such differences must be assumed tobe produced each by a single mutation. By tliis meansthe significance of the mutations may best be judged, andwhenever species difter from their nearest alUes in a higherdegree, the inference is allowed that they have been origin-ated by more than one mutation. Since the pubhcation of Darwins theory, the probabil-ity of such sudden changes playing an important part in theevolution of species has always found some support. Of late,the evidence has increased in this direction, especially underthe influence of Cope. Discontinuous evolution has beendefended among pakeontologists by Dollo, among zoolo-gists by Bateson, and among botanists by Korshinsky. ThisRussian author compiled the history of a large number ofvarieties from the widely scattered horticultural literatureand showed that, in almost all casesplantbreedingcom00vrie

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