Floral Biology of Mallotus oppositifolius (Euphorbiaceae)

Abstract

The unisexual flowers of Mallotus oppositifolius show a combination of entomophilous and anemophilous characteristics. They are visited by many species of short-tongued bees, but the powdery pollen is also presumably capable of wind dispersal. The female flowers offer no rewards to bees; it is therefore suggested that their resemblance to the pollen-yielding male flowers may cause bees to visit them in error. A NUMBER OF PLANTS OF THE TROPICAL FOREST UNDERSTORY have flowers that display combinations of characters normally associated with anemophily, such as light, smooth pollen, a high ratio of male to female flowers, and reduction of the attractive parts. However, air movement in the lower layers of the forest is very slight (Haddow and Corbet 1961), and it seems unlikely that pollen could be reliably transported for any distance (Faegri and van der Pijl 1971). Some forest Gramineae are visited and probably pollinated by insects (Soderstrom and Calderon 1971), and some forest Cyperaceae are visited by slugs (Lorougnon 1973). There are few published observations of pollination in such woody families as Euphorbiaceae that are frequent in the forest understory, particularly in disturbed places This paper reports observations on the common understory and forest edge shrub Mallotus oppositifolius (Geisel.) Muell. Arg. The observations were made in March 1977, at the beginning oif the rainy season, at the Agricultural Research Station of the University of Ghana, at Kade (60 09' N, 0? 55' W). The plants were growing at the edge of Moist Semi-deciduous forest (Hall and Swaine 1976). Five male and female inflorescences of various ages, giving a total of 220 flowers, were marked with numbered tags and observed each day.