1. The receptive tip of the carpel, which receives pollen at pollination and on which the pollen grain germinates. The stigma is adapted to catch and trap pollen, either by combing pollen off visiting insects or by various hairs, flaps, or sculpturings. The stigmas of certain plants show haptotropic movements. For example, the monkey flower (Mimulus guttatus) has a two-lobed stigma, which closes together when touched, so removing pollen from a visiting insect. The stigmas of wind-pollinated plants tend to be feathery or branched to increase the chances of pollination. The stigma usually secretes sticky substances, which may act as a pollen trap but may also be involved in the complex pollen/stigma compatibility interactions. The stigma and style act as physiological filters in controlling cross fertilization, although the actual mechanisms appear to be variable and little understood (see self incompatibility
). In members of the primitive angiosperm family Winteraceae the stigma is found along the margins of the ventral suture. In the closely related Degeneria vitiensis the margins of the carpel are not fused but are held together by interwoven papillae, which form the stigmatic surface. Studies of such plants have thrown light on the evolution of angiospermy.