Heterodostilism

Heterodostilism is a biological phenomenon observed in some plant species where an individual possesses two distinct types of flowers on the same plant, each with a different arrangement of reproductive organs. These floral morphs are typically distinguished by the relative lengths of their stamens and pistils. One type of flower, often referred to as "long-styled" or "pin-eyed," has a significantly longer pistil that extends beyond the stamens. Conversely, the other type, known as "short-styled" or "thrum-eyed," features stamens that are longer than the pistil.

This dimorphism in floral structure is a mechanism to promote outcrossing, the transfer of pollen between genetically different plants. The specific lengths of the stamens and pistils in each morph are thought to facilitate pollination by particular insect pollinators. For example, a pollinator visiting a long-styled flower will have its body dusted with pollen from the stamens located at a specific height. When this insect then visits a short-styled flower, the pollen is more likely to be deposited onto the stigma of the short pistil, and vice-versa. This reciprocal arrangement ensures that pollen is effectively transferred between flowers with compatible reproductive organ lengths, reducing the likelihood of self-pollination and increasing genetic diversity within the plant population. Heterodostilism is a form of heterostyly, a broader term encompassing variations in style length.