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Distyly in primroses. (A) Long-styled (pin) and short-styled (thrum) flowers of Primula vulgaris. (B) Vertically sectioned flowers, with the compatible pollinations indicated. (Pollen from high anthers is compatible with stigmas of long-styled plants, and pollen from low anthers is compatible with stigmas of short-styled plants, while the other two types of pollinations are incompatible.)
