Wolffia Horkel ex Schleid
Infl. in a cavity opening on the upper surface; one male and one female fl. together, without spathe. Ovule 1. Fr. spherical. Seed smooth; operculum prominent. Plants floating on water surface, budding from pouch at narrow end, platelets solitary or in twos. Platelets globose to ovoid, ± flat on top. Root absent. No red-purple pigment. About 8 spp., predominantly in tropical and subtropical areas.
Includes the world's smallest flowering plants, the individuals rarely exceeding 1 mm. in any direction. In suitable places plants form a continuous cover over large areas of water and after strong winds they may lie piled up in massive drifts along a shoreline.
