3) If the stimulus quality is high, and the stimulus threshold of an attracted wasp is low, pollinium removal will proceed (although more often the male will leave the flower after a short pause).
1) The pollinia hypothesis suggests that a switch from reward to deceit was possible given that the single transfer of a pollinium may yield high levels of fruit set.
The Marsdenieae are mainly separated from the Geropegieae by the absence of a hyaline insertion crest on the upper or outer edge of the pollinium (if present, it lies on the inner or lower edge of the pollinium), and the more or less complete absence of an outer corona (Bruyns & Forster, 1991; Omlor, 1998).
Kunze (1995) has shown that only this insertion crest becomes lodged in the guide rail and that growth of the pollen tubes takes place through the concave face of the pollinium.
The many pollinaria illustrated by Kupicha (1984) demonstrate clearly how variable the position of attachment of the caudicle to the pollinium may be in the Asclepiadeae: from the apex to near the middle of the outer edge.
1996) of the pellucid margin (hyaline insertion crest) on the pollinium is particularly worrisome.
Style head broad, often with flat or concave apex (rarely conical to slenderly conical), sessile on top of ovaries to tapering gradually with narrow neck into them, with 5 stigmatic zones located on sides of lower cylindrical part behind guide rails, secreting translator just above each guide rail; translator consisting of hard, cliplike, brown to black corpuscle, mostly with flanks and floor, with two flexible, translucent caudicles (rarely absent in some Marsdenieae), each of which attaches one pollinium to corpuscle; ovary apocarpous, mostl y superior.