The Origin of Species by Means of Natural Selection; Or, the Preservation of Favored Races in the Struggle for Life ...A.L. Burt, 1890 - 538페이지 |
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279 페이지
... fertility of a plant cannot be doubted ; for Gärtner gives in his table about a score of cases of plants which he castrated , and artificially fertilized with their own pollen , and ( excluding all cases such as the Leguminosa , in ...
... fertility of a plant cannot be doubted ; for Gärtner gives in his table about a score of cases of plants which he castrated , and artificially fertilized with their own pollen , and ( excluding all cases such as the Leguminosa , in ...
285 페이지
... fertility , both of first crosses and of hybrids , graduates from zero to perfect fertility . It is surprising in how many curious ways this gradation can be shown ; but only the barest outline of the facts can here be given . When ...
... fertility , both of first crosses and of hybrids , graduates from zero to perfect fertility . It is surprising in how many curious ways this gradation can be shown ; but only the barest outline of the facts can here be given . When ...
288 페이지
... fertility . These facts show how completely the fertility of a hybrid may be independent of its external resemblance to either pure parent . Considering the several rules now given , which govern the fertility of first crosses and of ...
... fertility . These facts show how completely the fertility of a hybrid may be independent of its external resemblance to either pure parent . Considering the several rules now given , which govern the fertility of first crosses and of ...
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adapted admit affinities allied species America ancient appear Asa Gray beak become bees believe belonging birds breeds cause cells characters climate closely allied color continued crossed crustaceans degree developed difficulty distinct species domestic doubt effects eggs embryo existing extinct extremely facts favorable females fertility flowers formation forms fossil Fritz Müller genera genus geological geological period gilt top Glacial period gradations greater number groups of species habits Hence hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living male mammals manner marsupials migration modified descendants natural selection naturalists nearly nest oceanic islands offspring organs parent peculiar perfect pigeons pistil pollen present principle probably produced quadrupeds ranked remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive suppose tend theory tion variability variations varieties vary whole widely different wings young