In spite of Sprengel's most patient and scientific research, that shed great light on the theory of natural selection a half century before Darwin advanced it, he never knew that flowers are nearly always sterile to pollen of another species when carried to them on the bodies of insect visitors, or that cross-pollenized blossoms defeat the self-pollinated ones in the struggle for survival. These facts Darwin proved in endless experiments.英文原著 · 《WILD FLOWERS》
A blooming plant, usually with many sterile shoots about its base, has an unkempt, untidy look; the seed capsules and the brown petals of withered flowers remaining among the bright yellow buds through a long season. No nectar is secreted by the St. John's-worts, therefore only pollen collectors visit them regularly, and occasionally cross-fertilize the blossoms, which are best adapted, however, to pollinate themselves.英文原著 · 《WILD FLOWERS》