Pollen morphology of Brazilian species of Cayaponia Silva Manso (Cucurbitaceae, Cucurbiteae)

The pollen morphology of 30 species of Cayaponia (Cucurbitaceae) from Brazil and one from Mexico is described. Pollen grains are large to gigantic in size (50->200 μm diameter), spheroidal or suboblate, 3- to 8-zonoporate or 4- to 10-pantoporate. The pori are operculate and have an annulus. The sexine is ornamented by variously sized spines and numerous interjacent pila; in some species the capita of the pila are fused. The sexine (pila) and the nexine 1 (foot layer) together are thicker than the nexine 2 (endexine). The species can be grouped based on pollen grain size, number of apertures, as well as pollen wall ornamentation into three pollen types and four subtypes. In addition to interspecific variation, intraspecific variation was also observed. Pollen identification is provided for species based on light microscopy.