Guayanese Arrowhead

The name has often been spelled guyanensis (K. Rataj 1972), which is incorrect. Sagittaria guayanensis was the spelling in the protologue. The holotype was collected by Humboldt and Bonpland in Colombia, not Guyana. The type citation is Colombia: Guainia: in wetlands near the sugar mill of Don Felix Farreras and the city of Bolivar. The type is supposedly at Paris, as with all HBK types; however, we (with the help of Alicia Lourteig) have been unable to locate it. MO has a fragment, however. Rataj did designate a neotype: Suriname, Hostman 870 (TCD!). The fragment at MO takes precedence over this neotype.

Sagittaria guayanensis was divided into two subspecies, S. guayanensis subsp. guayanensis from the Neotropics and subsp. lappula (D. Don) Bogin from the Paleotropics . The two subspecies were separated by the shape and size of the fruit in addition to their distribution. Sagittaria guayanensis subsp. lappula has compressed achenes longer than 2.5 mm, whereas subsp. guayanensis has plump achenes shorter than 2.5 mm (C. Bogin 1955).

A floating, fibrous-rooted herb with small rootstock. Leaves broadly ovate, membranous, indistinctly nerved, deeply cordate at the base, lobes and blade obtuse or rounded. Flowers white. Sepals appressed in fruit. Stamens 6-15. Achenes plump or compressed, with shallowly or deeply crested rarely smooth wings.

Distribution: Tropical America, tropical and subtropical Africa and Asia.

Lophotocarpus guayanensis (H.B.K.) J. G. Smith, Rep. Mo. Bot
Gard. 6 : 61. 1894.
Sagittaria guayanensis H.B.K. Nov. Gen. & Sp. 1 : 250. 1816. Echinodorus guyanensis Griseb. Fl. Brit. W. Ind. 505. 1864. Lophiocarpus guyanensis Micheli, in DC. Monog. Phan. 3: 62. 1881. Lophotocarpus guyanensis lypicus Buch. in Engler, Pflanzenreich 4 15 : 36. 1903.
Plants submerged ; leaves very variable in length, the petioles slender or stout, nodoseseptate, the blades ovate to suborbicular, 4-7 cm. long, obtuse or emarginate at the apex, the ovate basal lobes obtuse or abruptly pointed ; scapes often shorter than the leaves, with few rather approximate whorls ; sepals ovate, becoming 8-11 mm. long; fruit-bearing pedicels short and stout, often exceeded by the bracts; fruit-heads 12-15 mm. in diameter; achenes obovate, 2-2.5 mm. long, short-beaked, the margin tuberculate-crested all around, the faces tuberculate.
Type locality : Venezuela.
Distribution : Mexico and Central America ; Trinidad ; also in northern South America.

Sagittaria guayanensis, the Guyanese arrowhead, is an aquatic plant species. It is predominantly tropical, native to Mexico, Central America, the West Indies, and much of South America, as well as West Africa (from Senegal to Cameroon), south and southeast Asia (from Afghanistan to Taiwan to Indonesia), plus Sudan and Madagascar. It was unknown in the United States until a few populations were reported from Louisiana in 1969.

The epithet has incorrectly been spelled "guyanensis" by some authors. Type locale is not Guyana but rather in the Guayana region in what is now eastern Venezuela, regarded as part of Colombia when the specimen was collected.

Sagittaria guayanensis is a perennial herb with broadly hastate (arrow-shaped) leaves with ovate lobes.