Callitriche hermaphroditica
Callitriche heterophylla
autumn water-starwort, autumnal water-starwort, callitriche hermaphrodiate, northern water-starwort, scarlet waterstarwort
different-leaf water-starwort, diverse-leaf water-starwort, greater water-starwort, large water-starwort, prairie sandgrass, two-head water-starwort, variedleaf waterstarwort, 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, ± linear, tapering from near base or spatulate, 3.7–24.7 × 0.3–3.5 mm, 1+-veined.
bracts absent.
bracts caducous.
0 mm in fruit.
0 mm in fruit.
solitary;
styles erect, later recurved;
pollen colorless.
usually solitary;
styles erect or spreading;
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.
± round, (0.4–)0.5–0.9(–1.2) × 0.5–1(–1.2) mm, as long as wide;
mericarps black, not swollen, not winged or winged only at apex, wings straight, 0.05–0.1 mm wide.
= 6.
Callitriche hermaphroditica
Callitriche heterophylla
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.)
Two varieties have been recognized in Callitriche heterophylla, with var. bolanderi distinguished on the basis of its schizocarps being larger (for example, N. C. Fassett 1951b); however, the size of the schizocarps overlaps widely, and measurements of schizocarps from throughout North America show that there is no clear geographical or ecological separation between plants with smaller fruit and those with larger fruit. Therefore, there is no justification for maintaining the distinction.
Populations of small plants with linear leaves from parts of Canada and Alaska have been separated as Callitriche anceps. However, these appear to represent the lower extremes of variation in C. heterophylla, and morphological characters do not justify maintaining the distinction.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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