Callitriche hermaphroditica
Callitriche pedunculosa
autumn water-starwort, autumnal water-starwort, callitriche hermaphrodiate, northern water-starwort, scarlet waterstarwort
Nuttall's water-starwort
and leaf scales absent.
and leaf scales present.
not connate at base, ± linear, tapering from base, (7–)7.6–11.5 × 0.9–1.4 mm, 1-veined.
connate at base, obovate-oblanceolate to spatulate, (2.2–)2.7–5.7 × 0.7–2 mm, 2+-veined.
bracts absent.
bracts absent.
0 mm in fruit.
0–5 mm in fruit.
solitary;
styles erect, later recurved;
pollen colorless.
usually 1 staminate and 1 pistillate in 1 axil opposed by 1 pistillate, rarely both pairs at an axil with 1 staminate and 1 pistillate;
styles loosely ascending or ± reflexed;
pollen yellow.
1.1–1.9 × 1.2–2.4 mm, shorter than or as long as wide, sometimes longer than wide;
mericarps dark brown, not swollen, winged throughout, wings straight, 0.2–0.8 mm wide, as wide as or wider than mericarp body.
0.8–1 × 0.9–1.3 mm, shorter than wide;
mericarps black, not swollen, winged throughout, wings curled, giving appearance of thickened margins, 0.06–0.15 mm wide.
= 6.
= 20.
Callitriche hermaphroditica
Callitriche pedunculosa
Infraspecific divisions have been based on the size of fruit (for example, R. V. Lansdown 2006); assignment of North American populations to these taxa would be premature.
Callitriche autumnalis Linnaeus is a superfluous renaming of C. hermaphroditica, with which it is homotypic (R. V. Lansdown and C. E. Jarvis 2004).
Callitriche fassettii, C. hermaphroditica, and C. stenoptera are morphologically very close; however, C. hermaphroditica always has sessile fruit, whereas the fruit of both the other species may be pedicellate. The mericarp wing of C. stenoptera is consistently very narrow and that of C. fassettii is slightly wider than that of C. hermaphroditica, which is generally wide, particularly at the apex.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Callitriche nuttallii Torrey is an illegitimate, superfluous name that applies here. Torrey proposed it as a replacement for C. pedunculosa Nuttall based on the mistaken belief that the name by Nuttall was a later homonym of one by Arnott; the purported name by Arnott does not exist.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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USDA Plants Database- LBJ Wildflower Center
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