Rorippa crystallina
Rorippa subumbellata
Mackenzie River yellowcress
Lake Tahoe yellowcress, Tahoe yellow cress
(simple from base), erect, branched distally, 1–4 dm.
decumbent, much-branched distally, 0.5–2.5(–3) dm, (glabrous or pilose proximally).
rosulate;
[petiole (1.5–)3–7.7(–12) cm];
blade [(2.5–)4–14(–22) cm × (10–)20–40(–70) mm], margins dentate to crenate.
not rosulate;
blade margins subpinnatifid to sinuate.
petiolate or subsessile;
blade ovate to lanceolate, 2.5–7 cm × 4–13 mm (smaller distally), base cuneate, not auriculate, margins dentate.
sessile or shortly petiolate;
blade broadly oblanceolate to oblong, (lateral lobes oblong to ovate), 1–3.2 cm × 3–12 mm, base not or minutely auriculate, margins subpinnatifid to sinuate, or (lateral lobes) usually entire, (surfaces pilose or adaxially glabrous).
elongated.
(subumbellate), not or slightly elongated.
sepals (deciduous after anthesis), erect, oblong, 4–5 × 1–1.5 mm;
petals whitish, oblanceolate, 6–8 × 2.5–3 mm;
median filaments 3–4.2 mm;
anthers oblong, 0.8–1.2 mm.
sepals (persistent), erect, oblong or ovate, 2–3 × 1–1.5 mm;
petals yellow, spatulate to oblanceolate, 2.5–3.5 × 1–1.7 mm;
median filaments 2–2.5 mm;
anthers narrowly oblong, 0.8–1.2 mm.
divaricate to horizontal, straight, 12–20(–26) mm.
erect to divaricate-ascending, straight, 3–7(–9) mm, (pilose).
siliques, straight or slightly curved, linear, 14–26 × 2–2.8 mm;
ovules 28–40 per ovary;
style 0.3–1 mm.
silicles, straight, subglobose to broadly oblong, 3–6 × 2–3.5 mm;
valves glabrous;
ovules 30–44 per ovary;
style 0.8–1.5 mm.
uniseriate, brown, ovoid, 1.6–2 mm (1.2–1.5 mm diam.), colliculate.
biseriate, yellowish brown, angled, cordiform, 0.8–1.1 mm, strongly colliculate.
= 32.
Rorippa crystallina
Rorippa subumbellata
In his original description of Rorippa crystallina, Rollins considered the presence of calcium oxalate crystals in the plant to be a unique feature, but this was later found to be an artifact of treating the plants with formaldehyde (R. L. Stuckey 1972; R. C. Rollins 1993). Characterization of the species as native to Canada was questioned by G. A. Mulligan and W. L. Cody (1995), who believed that it was probably introduced from China. There is no species of mustard from elsewhere in the world that closely resembles R. crystallina, and it should be considered a Canadian endemic.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Of conservation concern.
Rorippa subumbellata appears to be restricted to Tallac and Truckee lakes and Lake Tahoe in eastern California (El Dorado and Placer counties) and western Nevada (Douglas County).
The record by Rollins of n = 5 for the species (see S. I. Warwick and I. A. Al-Shehbaz 2006) is highly unlikely; no such count is known in the entire tribe Cardamineae, to which Rorippa belongs.
Rorippa subumbellata is in the Center for Plant Conservation’s National Collection of Endangered Plants.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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USDA Plants Database
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