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.

Sagittaria demersa J. G. Smith, Rep. Mo. Bot. Gard. 6 ; 58. 1895
Plants submerged, but not greatly elongate ; leaves mere narrow phyllodia attenuate to the blunt apex from base 10-15 mm. in diameter; scapes usually 2-3 dm. long, simple, shorter than the leaves ; whorls of the inflorescence 4-6, the lower one with pistillate flowers; pedicels 1-3.5 cm. long; bracts 3-5 mm. long, partially united ; sepals oblong to ovate, becoming 4-4.5 mm. long; corolla about 1.5 cm. wide; filaments glabrous; anthers suborbicular ; fruit-head 5-6 mm. in diameter; achenes obovate, 1.5-2 mm. long, both margins winged, the beak lateral, erect, slender.
Type locality : Near Guerrero, Chihuahua, Mexico.
Distribution : Chihuahua.

Sagittaria demersa, commonly called Chihuahuan arrowhead, is an aquatic plant species native to north-central Mexico (Chihuahua, Durango. Hidalgo, Aguascalientes, Jalisco and Querétaro) and also from a few sites in the northern part of the US State of New Mexico (Mora and Colfax Counties).

Sagittaria demersa is an annual herb up to 60 cm tall. Leaves are flat, very long and narrow, up to 55 cm long but rarely more than 7 mm across. The plant occurs mostly submerged in streams and lakes.