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The production of a hermaphroditic floral type that opens at anthesis and may be visited by an insect vector, providing a means of cross-pollination.



pollination in flowers with an open perianth; an adaptation to cross-pollination. Many plants with chasmogamic flowers are still self-pollinators; for example, in peas and other papilionaceous plants chasmogamy may occur in the buds before the flowers open, and in Chamaenerion angustifolium chasmogamy may occur at the end of the flowering period, as a reserve method of pollination, in the event normal cross-pollination has not occurred. Self-pollination before the opening of the flower is the initial stage in the transition to cleistogamy, when the function has already changed (the plant has transferred to self-pollination), but the structure has remained as before (an open perianth).

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To establish baseline data on the size of Epifagus plants, large populations ([less than or equal to] 40 plants) were randomly sampled (all plant numbers ending in 2) and measured for the following morphological characteristics: plant height (cm), number of branches, number of chasmogamous and cleistogamous flowers, and distance (cm) to nearest host tree.
Chasmogamous flowers borne in pairs at tips of vegetative stems; bract subtending each flower like a vegetative leaf but generally smaller, 4-9 mm long, 1.
Date of first chasmogamous flower bud was also recorded, but this occurred over a much longer period of time.
Flowers are of two main types: chasmogamous flowers from the upper nodes, and cleistogamous flowers from nodes near or below ground level (Hunt, 1975).
Listia were reported to be chasmogamous by Van Wyk (1991).
These include pathogen-induced castration of a host's chasmogamous flowers (Clay 1991), the alteration of pollinator behavior caused by floral mimicry by pathogens (Roy 1993), patterns of pathogen transmission which can be related to the probabilities of colonization and extinction of host populations (Antonovics 1994), and the direct loss of fruits from a variety of rots and mildews (Rawal 1993, Duffy and Gardner 1994).
Differences in fitness between seedlings derived from cleistogamous and chasmogamous flowers in Impatiens capensis.
linearis in many locations, and is unique in the genus for producing salmon to yellow chasmogamous flowers as well as minute whitish cleistogamous flowers.
For example, self-pollination and cleistogamous flowers (closed flower structure) severely reduce gene flow between populations, while cross-pollination and chasmogamous flowers (open flower structure) may facilitate significant gene flow between populations.
Third, mixed cleistogamous selfing and chasmogamous outcrossing can evolve when the resulting two seed types are dispersed to microhabitats with different selective pressures (Schoen and Lloyd 1984).
With respect to Danthonia we predict that outcrossed chasmogamous progenies will, on average, contain a higher frequency of resistant progeny than self-fertilized cleistogamous progenies when inoculated with the maternal fungal strain [ILLUSTRATION FOR FIGURE 1 OMITTED].
Development of cleistogamous and chasmogamous flowers in Lamium amplexicaule (Labiatae)--Example of heteroblastic inflorescence development.