Heredity / by J. Arthur Thomson.

  • John Arthur Thomson
Date:
1920
Catalogue details

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

Credit: Heredity / by J. Arthur Thomson. Source: Wellcome Collection.

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    ASEXUAL MULTIPLICATION 35 the fisherman tears asunder, may give rise to several new in¬ dividuals. From nine excised fragments of a single Planarian worm, Voigt reared nine individuals {see Weismann, 1904, vol. ii. p. 25). Similarly, in regard to plants, many of the simpler multi¬ cellular forms produce detachable buds, familiar in the case of the liverworts ; and even in the flowering plants the same may occur, as in the bulbils of the tiger-lily. As in animals, great colonies may be formed, consisting of many individuals materially continuous, well seen in strawberries, whose creeping stems root here and there and give rise to independent plants. It is also a Fig. 4.— Comet-form of Starfish, showing how one arm regenerates the other four. (After Haeckel.) familiar fact that cut-off portions of a plant may readily give rise to entire individuals ; a little piece of moss, a Begonia leaf, a corner of a potato tuber—and hundreds of instances might be given—will sufñce to start a new plant. In many ways the whole vegetable kingdom seems comparable to the sedentary sections of the class Ccelentera among animals (zoophytes, sea-anemones, corals, etc.), e.g. in the various forms of alternation of generations which occur, and in the readiness with which representative fragments will regrow the whole. This capacity of regenerating the whole from a small piece is the more striking when there is considerable differentiation of tissues and organs, as there is in flowering plants and the higher animals. The