Alisma

Linnaeus

Sp. Pl. 1: 343. 1753; Gen. Pl. ed. 5; 160, 1754.

Common names: Water-plantain
Etymology: ancient Greek name, adopted by Linnaeus from Dioscorides
Treatment appears in FNA Volume 22.
 TaxonIllustrator 
FNA22 P5 Sagittaria Alisma Hydrocharis pg 21.jpegSagittaria latifolia
Alisma subcordatum
Hydrocharis morsus-ranae
John Myers
John Myers
John Myers

Herbs, perennial, submersed, floating-leaved, emersed, glabrous; rhizomes often present; stolons absent; corms absent; tubers absent. Roots not septate. Leaves sessile or petiolate; petiole triangular; blade with translucent markings absent, linear to ovate, base attenuate to rounded, margins entire, apex obtuse to acute. Inflorescences panicles, of 2–10 whorls, erect, emersed, rarely submersed; bracts delicate, smooth, apex acuminate, surfaces smooth. Flowers bisexual; pedicels ascending; bracts subtending pedicels, lanceolate, shorter than pedicels, apex acuminate; receptacle flattened; sepals erect, not sculptured, herbaceous; petals pink or white, entire; stamens 6–9, filaments filiform, glabrous; pistils 15–20, in ring around margin of flattened receptacle, not radiating in starlike pattern, distinct; ovules 1; styles lateral. Fruits without longitudinal ribs, strongly laterally compressed, abaxial wings absent, lateral wings absent, abaxially 2–3-ribbed, abaxial keel absent, glands absent. x = 7.

Distribution

Widely distributed, nearly worldwide

Discussion

Much controversy surrounds the treatment of Alisma in North America. At present three distinct native species in North America are generally recognized (P. Rubtzoff 1964) as well as the probable occurrence of two introduced species, one in California and the other in Alaska.

Species 9 (5 in the flora).

Key

1 Style longer than or (equal to) ovary; anthers ellipsoid. > 2
1 Style shorter than or (equal to) ovary; anthers ovoid to rounded. > 3
2 Petals with obtuse apex, purplish white to purplish pink; style ± straight; leaf blade ovate to broadly lanceolate; Alaska. A. plantago-aquatica
2 Petals with acute apex, purplish pink; style curved proximally; leaf blade narrowly elliptic to lanceolate; California. A. lanceolatum
3 Achenes with 2 abaxial grooves, 1 abaxial ridge; leaves submersed, ribbonlike, or if emersed, blades linear-lanceolate to narrowly elliptic. A. gramineum
3 Achenes with1 abaxial groove; leaves emersed, rarely submersed or floating, blades ovate to elliptic. > 4
4 Fruiting heads 2–4 mm diam.; achenes 1.5–2.2 mm; petals 1–3 mm. A. subcordatum
4 Fruiting heads 4.1–7 mm diam.; achenes 2.1–3 mm; petals 3.5–6 mm. A. triviale
... more about "Alisma"
acuminate +, obtuse +  and acute +
Robert R. Haynes +  and C. Barre Hellquist +
Linnaeus +
attenuate;rounded +
linear +  and ovate +
lanceolate +
Water-plantain +
Widely distributed +  and nearly worldwide +
u--shaped +
ancient Greek name, adopted by Linnaeus from Dioscorides +
subsessile +  and long-pedicellate +
hypogynous +
compressed +
decumbent +  and floating +
submersed +  and emersed +
petiolate +  and sessile +
emersed +, floating +  and submersed +
decumbent +  and floating +
white +  and pink +
deciduous +
triangular +
not radiating +
decumbent +  and floating +
bj1968a +, hendricks1957a +, rubtzoff1964a +  and voss1958a +
not septate +
persistent +
not sculptured +
Alismataceae +
emersed +  and submersed +
bracteolate +  and branching +