Trapa L.

Floating aquatic herbs with dimorphic leaves, submerged ones opposite pinna-tifid rootlike, apical ones in a rosette, rhomboid, dentate, with spongy often inflated petiole, arranged in leaf-mosaic; stipules 4-8, minute. Flowers bisexual, small, solitary, axillary, short-pedicelled, 4-merous, white or lilac. Petals imbricate. Disk present. Ovary half-inferior with 1 style and 2-4 persistent sepals turning often to thorns or horns. Fruit mostly 1-celled, 1-seeded, shell bone-hard; thorns after withering often set with barbs at the apex. Seed often producing 2-5 free germ-stalks.

Trapa is very rare and was for the first time reported in 1877 in Java. It is surely a component of the old lowland euthrophous swamp flora such as is preserved in the Danoe swamp (Bantam).

Uses. The fat-containing kernels of T. bicornis are highly nutritious and are eaten in West Java but not on a scale comparable to that of several parts of Asia, where it is a staple food.