Sagittaria sinensis Sims
Aquatic, glabrous herb with thick stolons bearing tubers at tip. Leaves mostly emerged, upright, sagittate or somewhat hastate, blade ovate or linear-lanceolate, (5-6.5-) 8-17 cm long along midrib, (1.5-2.5-) 5-7 cm broad, acute, basal lobes triangular or linear-lanceolate, often longer than the blade, sharply acute; petiole 60-75 cm long, triangular. Inflorescence an unbranched scapose raceme, 30-50 cm long. Flowers in 2-6 whorls of (2-) 3 (-5) flowers each, unisexual, 1-2 cm across, white; pedicels 8-15 mm long, short in females; bracts triangular-ovate, 8-10 mm long, 3-4 mm broad, acute-acuminate. Sepals elliptic, 6-8 mm long, 5-6 mm broad, somewhat keeled, margins broadly membranous, reflexed in fruit. Petals broadly elliptic-suborbicular, 12-15 mm long 12-15 mm broad, white, without basal purple spot. Stamens c. 20, filaments lanceolate, 1.5-2 mm long; anthers yellow, oblong, as long as the filaments. Head of achenes subglobose, c. 1 cm across; achenes triangularly obovate, with laterally bent beak. c. 2-3 mm long, wings subcrenate to entire.
Holotype: Described from China, Petiver, Gazoph. tab. 19, fig. 5. 1702.
Distribution: Widespread from Iraq through Iran and West Pakistan eastwards to China, Malaysia and Japan; introduced and adventive in Australia, Hawaii, Fiji, Philippines, Borneo and Java.
It differs from the European and North Asian Sagittaria sagittifolia Linn. in having pure white petals with no basal purple spot, yellow rather than purple anthers, reflexed rather than spreading sepals and very acute rather than blunt tips to the basal lobes of the leaf which are often longer than the blade.
This species exhibits much variation in leaf shape and flower size etc. as is mostly the case with aquatic plants. These variants do not deserve taxonomic status.
The plant is cultivated in China and Japan for starch-containing tubers which have been used in a variety of cooked and fresh dishes for centuries. It was probably introduced by Chinese to Hawaii, Indonesia and the Philippines on account of its food value. Aerial parts are fed to cattle in parts of India and southeast Asia. It is not put to any use in Pakistan.