Sagittaria rigida
Sagittaria guayanensis
Canadian arrowhead, sagittaire dressee, sessile-fruit arrowhead
guyanese arrowhead
emersed or submersed; submersed leaves phyllodial, flattened, 30–70 cm, rarely widening into blade; emersed leaves phyllodial, flattened, or petiole triangular, 34–50 cm, blade linear to elliptic, rarely hastate to sagittate, 5–15 × 0.6–12 cm, basal lobes when present shorter than remainder of blade.
racemes, of 2–8 whorls, emersed, 8–10 × 2–6 cm;
peduncles 10–115 cm;
bracts connate more than or equal to ¼ total length, ovate, 3–6 mm, delicate, not papillose; fruiting pedicels absent.
to 3 cm diam.;
sepals recurved, not enclosing flower;
filaments dilated, shorter than anthers, pubescent;
pistillate sessile to subsessile, without ring of sterile stamens.
heads 1–1.7 cm diam.;
achenes obovoid to oblong, abaxially keeled, 2–3 × 1.3–1.6 mm, beaked;
face not tuberculate, wings 1–2, ± entire, glands 1;
beak lateral, recurved, 0.8–1.4 mm.
= 22.
Sagittaria rigida
Sagittaria guayanensis
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).
Subspecies 2 (1 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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