keys to the vascular plants of east texas - Botanical Research ...

ALISMA/ALISMATACEAE
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1. Pistils (later, achenes) in a single ring around the margin of a flattened receptacle; stamens 6; leaf
blades never sagittate (instead, cuneate to cordate at base); petals 1–3 mm long __________________ Alisma
1. Pistils (later, achenes) densely crowded over entire surface of a convex receptacle, forming a
head-like mass; stamens usually � 6 (often numerous); leaf blades variable in shape, sometimes
sagittate; petals (1–)3–20(–25) mm long.
2. Fruiting “heads” (actually aggregate of achenes from a single flower) rough in appearance,
resembling a bur due to the conspicuous persistent styles on the achenes; achenes turgid,
ribbed or ridged, not winged; flowers perfect; leaf blades never sagittate ________________ Echinodorus
2. Fruiting “heads” not bur-like (except somewhat so in S. brevirostra); achenes flattened, with a
membranous lateral wing; flowers perfect or imperfect, at least the lower imperfect; leaf blades
sagittate OR not so ______________________________________________________________ Sagittaria
ALISMA L. WATER-PLANTAIN
AA widely distributed but primarily n temperate and Australian genus of 9 species (Haynes
& Hellquist 2000a). (Greek: alisma, water-plantain)
REFERENCES: Fernald 1946a; Hendricks 1957[1958]; Voss 1958; Pogan 1963; Rubtzoff 1964;
Björkqvist 1967, 1968.
Alisma subcordatum Raf., (slightly cordate), SOUTHERN WATER-PLANTAIN, AMERICAN WATER-
PLANTAIN, WATER-PLANTAIN, SMALL-FLOWER WATER-PLANTAIN, MUD-PLANTAIN, SUBCORDATE WA-
TER-PLANTAIN. Emergent perennial herb with numerous fibrous roots; stems erect; leaves basal,
emersed, rarely floating; leaf blades ovate to elliptic, to 12(–15) cm long and 8(–10) cm wide, basally
broadly cuneate to subcordate, long-petioled; inflorescences to 60(–100) cm tall, paniculate,
with whorled branches; flowers perfect; petals white or pinkish, 1–3 mm long, suborbicular;
receptacle flattened, 4 mm wide or less including achenes; style 1/4 the length of the ovary;
achenes 1.5–2.2 mm long, wingless, smooth, with a single dorsal groove. Shallow water; Lamar
(Carr 1994) and Red River (Turner et al. 2003) cos. in the Red River drainage; also Hemphill Co.
in the Panhandle (BRIT); Hatch et al. (1990) also cited the Blackland Prairie; se Canada and
throughout e U.S. (except FL and LA) w to ND and TX, also AZ, CA, NM, and OR. Jun–Sep. [A.
parviflorum Pursh, A. plantago-aquatica L. var. parviflorum (Pursh) Torr., A. plantago-aquatica
subsp. subcordatum (Raf.) Hultén] While not officially designated as such (e.g., TOES 1993; Carr
2002d; Poole et al. 2002), given its limited distribution in the state, we consider this species to be
of conservation concern in TX. �
ECHINODORUS Rich. ex Engelm. BURHEAD
Ours emergent annual or perennial herbs; emersed leaves long-petioled, the leaf blades with arcuate
veins prominent below; submersed leaves also sometimes present, usually sessile; inflorescences
usually much exceeding the leaves, racemose or umbellate, with flowers in whorls;
flowers perfect; petals white; stamens ca. 9–22; pistils 15–250, spirally arranged on a convex receptacle
forming a head-like mass; fruiting “heads” rough in appearance, resembling a bur due
to the conspicuous persistent styles on the achenes; achenes turgid, ribbed or ridged, beaked,
without a wing.
AA genus of 26 species extending from the n U.S. to Argentina and Chile (Haynes & Holm-
Nielsen 1994; Haynes & Hellquist 2000a). A narrowly endemic species, E. floridanus R.R. Haynes
& J.R. Burkhalter, was recently described from the Florida Panhandle (Haynes & Burkhalter
1998). Some are cultivated as ornamental aquarium plants or aquatic ornamentals. Bees were
found to be the main pollinators of a South American species (Vieira & de Souza Lima 1997),
and given the showy flowers of East TX species, insect pollination is expected. (Greek: echinus,
rough husk, and doros, a leather bottle, applied to the ovary, which in most species is armed
with the persistent style (= beak), these giving the fruiting “heads” a bur-like appearance)
REFERENCES: Fassett 1955; Rataj 1975; Haynes & Holm-Nielsen 1986; Haynes & Burkhalter 1998.