Sagittaria rhombifolia Cham.

  • Authority

    Bogin, Clifford. 1955. Revision of the genus Sagittaria (Alismataceae). Mem. New York Bot. Gard. 9 (2): 179-233.

  • Family

    Alismataceae

  • Scientific Name

    Sagittaria rhombifolia Cham.

  • Description

    Species Description - Perennial with horizontal rhizome. Leaves typically emersed, occasionally submerged or floating, with linear to ovate blades 8-25 x 0.5-6 cm, the infrequent floating blades cordate, the petioles 15-90 cm long or longer. Scapes simple, 20-90 cm long, with 3-10 whorls of flowers. Bracts large, 1.2-3 x 0.4-0.9 cm, thickened, connate at the base, attenuate, those of the upper whorls somewhat overlapping and appressed to scape. Pistillate flowers with pedicels strongly recurved, markedly thickened, 1.5-4 cm long, occasionally with a ring of functional stamens; sepals 1-2 x 1-2.5 cm, closely appressed to the receptacle at maturity; petals 1.5-2.5 x 1-2 cm, all white or with a purple spot at the base. Staminate flowers with pedicels filiform, divaricate, 2.5-8 cm long; stamens numerous, the filaments linear, glabrous to minutely glandular-pubescent, 2-3 mm long, the oblong anthers only 0.5-1.2 mm long. Mature pistillate heads 1.5-2.5 cm in diameter; achenes large 2.5-5.5 x 1.3-2.5 mm, very narrowly winged, obovate, abruptly tapering to a slender base, the faces unadorned, the beak 0.5-1 mm long, horizontally or obliquely inserted.

  • Discussion

    Sagittaria affinis Seub. in Mart. Fl. Bras. 3(1): 111. 1847.

    Sagittaria lagoensis Seub. & Warm. Vidensk. Meddel. Naturh. Foren. Kjoeb. 1872: 113. 1872.

    Sagittaria rhomboidalis Micheli in DC. Monogr. Phan. 3: 66. 1881. Error for rhombifolia.

    Sagittaria pugioniformis var. platyphylla Micheli in DC. Monogr. Phan. 3: 78. 1881.

    Sagittaria pugioniformis var. affinis (Seub.) Kuntze, Rev. Gen. 3: 328. 1898.

    Sagittaria pugioniformis var. rhombifolia (Cham.) Kuntze, Rev. Gen. 3: 328. 1898.

    Sagittaria amazonica Huber, Bol. Mus. Goeldi 5: 314. 1909.

    Sagittaria cordifolia Suess. & Beyerle, Repert. Sp. Nov. 39: 17. 1935.

    Sagittaria pugioniformis Auct. non L.

    Type collection: Sellow s.n., Brazil (holotype not seen, presumably at Berlin; iso type K).

    A widespread but seldom collected tropical species of shallow waters of lakes, swamps, and quiet waterways. The wide variation in leaf outline is seemingly the only basis for the proposed synonyms. The thickened, recurved pedicels, the closely appressed sepals, the occasional rings of functional stamens in the pistillate flowers, and the purely tropical distribution serve to relate S. rhombifolia most closely with S. montevidensis and S. guyanensis. The species superficially resembles S. montevidensis subsp. cbilensis; however, the overlapping, appressed bracts, the large, unadorned achenes, the non-sagittate leaves and the geographical distribution are all quite distinct.

    All authors since Linnaeus have ascribed this species to S. pugioniformis L. Close examination of a photograph of the Linnaean type specimen of S. pugioniformis shows that it has no relation to S. rhombifolia except for the similarly narrowed leaves. The Linnaean type is obviously the narrow-leaves form of S. lancifolia L. (S. angustifolia Lindl.), showing the typical reflexed sepals and ascending pedicels of the pistillate flowers of the subgenus Sagittaria.

  • Distribution

    Lowlands of tropical South America. Collections examined from Bolivia, British Guiana, Brazil, Colombia, Paraguay, Venezuela.

    Colombia South America| French Guiana South America| Suriname South America| Guyana South America| Venezuela South America| Ecuador South America| Peru South America| Bolivia South America| Paraguay South America| Brazil South America|