POLLEN

Anthers of Philodendron (Grayum, 1991) have a two or more layer tapetum of a paraplasmodial type. The pollen mother cell cytokinesis is probably successive.

Philodendron pollen is binucleate (Zavada, 1983; Grayum, 1985, 1986, 1992) inaperturate, starchy and of moderately large size (averaging 40ðmm, ranging 28ðmm-40ðmm) with subisopolar polarity (Grayum, 1985; 1991). As in most aroid genera, it is shed in monads. Pollen is typically boat-shaped-elliptic to oblong, or occasionally elongate as in P. radiatum. It is usually round in cross-section but may be very obscurely keeled in P. hederaceum to moderately keeled in P. jacquinii, P. jodavisianum, and P. wendlandii or prominently keeled in P. mexicanum. The exine sculpturing is largely psilate, sometimes minutely verruculate, scabrate or fossulate (P. fragrantissimum, P. grandipes, P. jacquinii, P. jodavisianum, and P. pterotum) to clearly punctate, subfossulate, subfoveate or subverrucate (P. mexicanum and P. wendlandii).