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acters albida already amongst annual plants appeared arise arisen arose biennial biennial plants biennis bracts breeders brevistylis buds carpels char characters constant cotyledons crop crossing crumples cultivated cultures curve Darwin deviations Draba verna dwarfs elementary species elliptica example exhibited existence experiments fact fasciation fertilized field at Hilversum flowering plants flowers fluctuating forms fruit-length fruits garden genera germinated gigas give rise groups harvest Hilversum hybridization inflorescence investigation laevifolia lata lateral branches leaf leaves length leptocarpa main stem maize manuring marckiana mean muricata muta mutability mutation mutation theory nanella natural selection number of individuals nutrition oblonga observed occur Oenothera Lamarckiana origin of species Pangenesis parent species partly period petals pollen question race result rosettes rubrinervis scintillans seed-parents seedlings self-fertilized single sowing sown square meters subspecies theory of descent theory of selection tion tricotyls umbel variability variation varieties whilst whole wild young plants
Page 34 - ... I am fully convinced that species are not immutable; but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species, in the same manner as the acknowledged varieties of any one species are the descendants of that species. Furthermore. I am convinced that Natural Selection has been the most important, but not the exclusive, means of modification.
Page 3 - By the mutation theory I mean the proposition that the attributes of organisms consist of distinct, separate and independent units. These units can be associated in groups, and we find, in allied species, the same units and groups of units.
Page 86 - I cannot doubt that during millions of generations individuals of a species will be born with some slight variation profitable to some part of its economy ; such will have a better chance of surviving, propagating this variation, which again will be slowly increased by the accumulative action of natural selection ; and the variety thus formed will either coexist with, or more commonly will exterminate its parent form.
Page 4 - According to the Mutation theory individual variation has nothing to do with the origin of species. This form of variation, as I hope to show, cannot even by the most rigid and sustained selection lead to a genuine overstepping of the limits of the species and still less to the origin of new and constant characters.
Page 250 - Icevifolia and O. brevistylis to maintain themselves in the spot where they arose — mere scattered examples among the host of Lamarckianas which surround them; and, what is more, pure in respect of all their characters ( apart of course from accidental crossing ) . That the struggle for existence is a pretty keen one in the 'field in question may be gathered from the fact that a vigorous Lamarckiana can bear 100 fruits and that each fruit contains between 200 and 300 seeds. The whole...
Page 583 - The contents of the book include a readable and orderly recital of the facts and details which furnish the basis for the mutation-theory of the origin of species. All of the more important phases of heredity and descent come in...
Page 255 - The new species fall right outside the range of this variability; as is evident from the fact that they are not connected with the parent type by intermediate or transitional forms. New races can of course be evolved by repeated selection in one or another direction in Lamarckiana just as much as in any other plant. Indeed I have, myself, produced a long-fruited and a short-fruited form in this way. But such races remain dependent on selection and differ from their type only in one feature: they...
Page 219 - I really had hit upon a plant in a mutable period liecame evident from the discovery, which I made a year later, of two perfectly definite forms which were immediately recognizable as two new elementary species. One of them was a short-styled form : O. brevistylis, which at first seemed to be exclusively male, but later proved to have the power, at least in the case of several individuals, of developing small capsules with a few fertile seeds. The other was a smooth-leaved form with much prettier...