CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF VARIETIES--INFLUENCE OF
DOMESTICATION ON FERTILITY.
DIFFICULTIES IN JUDGING OF THE FERTILITY OF VARIETIES WHEN CROSSED--VARIOUS
CAUSES WHICH KEEP VARIETIES DISTINCT, AS THE PERIOD OF BREEDING AND SEXUAL
PREFERENCE--VARIETIES OF WHEAT SAID TO BE STERILE WHEN CROSSED--VARIETIES
OF MAIZE, VERBASCUM, HOLLYHOCK, GOURDS, MELONS, AND TOBACCO, RENDERED IN
SOME DEGREE MUTUALLY STERILE--DOMESTICATION ELIMINATES THE TENDENCY TO
STERILITY NATURAL TO SPECIES WHEN CROSSED--ON THE INCREASED FERTILITY OF
UNCROSSED ANIMALS AND PLANTS FROM DOMESTICATION AND CULTIVATION ... Page
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