HETEROSTYLY AND INCOMPATIBILITY IN VILLARSIA CAPITATA (MENYANTHACEAE)

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Abstract
Summary: Villarsia capitata, a diploid annual of Western Australia, has distylous flowers. Results of a crossing program indicate that its distyly is associated with an incompatibility system. Intramorph pollinations produced 0.4‐0.8 seeds per pollination; intermorph pollinations produced 10.2 seeds per pollination in pins and 3.3 in thrums. About sixty percent of pin ovules and twenty percent of thrum ovules mature to seed following intermorph pollinations. These differences may result from the smaller size of thrum stigmas, from greater difficulty in transferring pollen to thrum stigmas in artificial pollinations, or from unknown causes. Villarsia capitata is a highly specialized member of the genus in its capitate, bracteate inflorescences and its annual habit, yet it retains a breeding system that is primitive in the Menyanthaceae.

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