Chihuahuan Arrowhead

Sagittaria demersa was known previously only from central Mexico. It is known in the United States from three recent collections taken in northern New Mexico.

Herbs, annual, to 60 cm; rhizomes absent; stolons present; corms present. Leaves submersed, phyllodial, lenticular, to nearly terete, 12--53 ´ 0.3--0.7 cm; rare stranded plants without expanded leaf blades. Inflorescences racemes, of 2--7 whorls, floating or emersed, to 16 ´ 4 cm; peduncles 13.5--28 cm; bracts connate more than ¼ total length, ovate to lanceolate, 1.5--2 mm, delicate, not papillose; fruiting pedicels spreading to reflexed in flower and fruit, cylindric, 1.5--6.5 cm. Flowers 1.5--5 cm diam.; sepals spreading in staminate, appressed to spreading in flower and fruit in pistillate, often enclosing flower or fruiting head; filaments dilated, longer than anthers, glabrous; pistillate pedicellate, without ring of sterile stamens. Fruiting heads 0.4--0.6 cm diam; achenes oblanceoloid to obovoid, not abaxially keeled, 1.5 ´ 1 mm, beaked; faces not tuberculate, wings absent, glands absent; beak lateral, erect, 1.1 mm.

N.Mex.; c Mexico.

Flowering summer--fall.

Streams and lakes; 1500--2000m.