The image shows pin(smaller)and thrum(larger) pollen grains of Primula vulgaris Huds stained with lactophenol cotton blue and observed under an optical microscope at x40 magnification. Primula vulgaris is a distylous species, meaning it has two distinct morphs (pin and thrum) with hermaphrodite flowers coexisting in a population. The two types of pollen on a single stigma seen in the image represent cross pollination (i.e pin pollen on a thrum stigma) and self pollination(i.e pin pollen on a pin stigma occurring within the same plant).
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