Flora of North America species comparison

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Sagittaria filiformis

Sagittaria guayanensis

narrow-leaf arrowhead, threadleaf arrowhead

guyanese arrowhead
Habit Herbs, perennial, to 170 cm, mostly of fresh waters, some plants stranded along shore; rhizomes absent; stolons present; corms present.
Leaves

submersed or floating, rarely emersed; submersed phyllodial, flattened, 30–250 × 0.1–1.5 cm; floating with petiole flattened, to 40 cm, blade linear-ovate to ovate, rarely sagittate, to 3.5 × 0.5 cm; emersed with petiole 5–10 cm, blade linear-ovate to ovate, rarely hastate to sagittate, to 4 × 0.5 cm; stranded plants usually with expanded leaf blades.

Inflorescences

racemes, rarely panicles, of 4–10 whorls, floating to slightly emersed, 15–25 × 5–15 cm;

peduncles 10–200 cm;

bracts connate more than ¼ total length, lanceolate, 110 mm, delicate, not papillose; fruiting pedicels spreading to recurved, cylindric, 1.5–4.5 cm.

Flowers

to 3 cm diam.;

sepals spreading in staminate, erect in pistillate, enclosing flower or fruiting head;

filaments dilated, ± equaling anthers, glabrous;

pistillate pedicellate, without ring of sterile stamens.

Fruiting

heads 0.7–1 cm diam.;

achenes obovoid, abaxially keeled, 5 × 2.5 mm, beaked;

faces not tuberculate, wings 0–3, ± entire, glands 0–1;

beak lateral, erect, 1 mm.

2n

= 22.

Sagittaria filiformis

Sagittaria guayanensis
Phenology Flowering summer–fall.
Habitat Shallow, swift waters or deep streams in northern portion of range, ponds, lakes, drainage canals, and swamps in southern portion of range
Elevation 0–100 m (0–300 ft)
Distribution
from FNA
AL; CT; FL; GA; MA; ME; NC; NJ; NY; PA; RI; SC; VA
[WildflowerSearch map]
[BONAP county map]
from FNA
LA; Mexico; West Indies; tropical regions; Asia; Africa [Introduced, North America]
[BONAP county map]
Discussion

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.)
Source FNA vol. 22. FNA vol. 22.
Parent taxa Alismataceae > Sagittaria Alismataceae > Sagittaria
Sibling taxa
S. ambigua, S. australis, S. brevirostra, S. cristata, S. cuneata, S. demersa, S. engelmanniana, S. fasciculata, S. graminea, S. guayanensis, S. isoetiformis, S. kurziana, S. lancifolia, S. latifolia, S. longiloba, S. montevidensis, S. papillosa, S. platyphylla, S. rigida, S. sanfordii, S. secundifolia, S. subulata, S. teres
S. ambigua, S. australis, S. brevirostra, S. cristata, S. cuneata, S. demersa, S. engelmanniana, S. fasciculata, S. filiformis, S. graminea, S. isoetiformis, S. kurziana, S. lancifolia, S. latifolia, S. longiloba, S. montevidensis, S. papillosa, S. platyphylla, S. rigida, S. sanfordii, S. secundifolia, S. subulata, S. teres
Subordinate taxa
S. guayanensis subsp. guayanensis
Synonyms S. stagnorum, S. subulata var. gracillima
Name authority J. G. Smith: N. Amer. Sagittaria. 20, plate 15, figs. 5–8. (1894) Kunth: in A. von Humboldt et al., Nov. Gen. Sp. 1: 250. (1816)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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