Nasturtium
Nasturtium gambelii
watercress, yellowcress
Gambel's water cress, Gambel's yellowcress
prostrate or decumbent, or erect in emergent plants, unbranched.
5–12 dm.
cauline;
not rosulate;
petiolate;
petiole base sometimes auriculate, blade (pinnately compound in emerged plants, or simple in deeply submerged plants, lateral leaflets petiolulate or sessile, 1–6(–12) pairs), margins entire, repand, or, rarely, dentate.
petiole narrowly winged, base auriculate or not;
blade 9–17-foliolate, 3–10 cm;
lateral leaflets sessile, rachis narrowly winged, blade about same size as terminal;
terminal leaflet blade linear to narrowly oblong or lanceolate, 0.5–2.5 cm × 2–8(–10) mm, base decurrent with adjacent pair of leaflets, margins often dentate, rarely sinuate-repand, apex acute.
(corymbose, several-flowered), elongated in fruit.
sepals erect or ascending, oblong [ovate], lateral pair subsaccate or not saccate basally, (glabrous);
petals usually white, rarely pink, obovate or narrowly spatulate, (longer than sepals), claw undifferentiated from blade, (attenuate to clawlike base, apex obtuse, acute, or rounded);
stamens tetradynamous;
filaments (white), not dilated basally;
anthers oblong, (apex obtuse);
nectar glands (2), lateral, annular or semiannular.
sepals 3–4 × 1–1.5 mm;
petals white, spatulate or oblanceolate, 6–8 × 2–2.5 mm, (base to 2 mm), apex obtuse to acute;
filaments 5–7 mm;
anthers 1–1.2 mm.
divaricate or descending, slender, (glabrous or adaxially puberulent).
divaricate or descending, straight, 9–25 mm.
siliques, sessile, usually linear, rarely narrowly oblong, smooth or slightly torulose, straight or slightly curved, terete;
valves each obscurely veined, glabrous;
replum rounded;
septum complete;
ovules 25–50 per ovary;
style obsolete or distinct;
stigma capitate.
2–3 cm × 1–1.2 mm;
ovules 24–40 per ovary;
style 1–2.5 mm.
plump, not winged, oblong or ovoid;
seed coat (minutely to coarsely reticulate), not mucilaginous when wetted;
cotyledons accumbent.
uniseriate, reddish brown, ovate, 1–1.2 × 0.6–0.8 mm, minutely reticulate with 300–450 areolae on each side.
= 8.
Nasturtium
Nasturtium gambelii
Species 5 (4 in the flora).
There has been considerable disagreement as to whether Nasturtium should be maintained as a distinct genus or be united with Rorippa. Molecular data and a critical evaluation of morphology (I. A. Al-Shehbaz and R. A. Price 1998) clearly show that Nasturtium is much more closely related to Cardamine than it is to Rorippa, and that the two genera should not be united.
Plants of Nasturtium floridanum, N. microphyllum, and N. officinale typically produce compound leaves when submerged in shallow waters or when their branches are emergent. When submerged in deep waters, all three produce simple leaves, and, in that case, it is impossible to distinguish them. The hybrid between N. officinale and N. microphyllum, N. ×sterilis Airy Shaw, is uncommon in North America, having been reported from Connecticut, Idaho, Michigan, and New Hampshire (P. S. Green 1962), and is far more common in Europe, where it has recently been studied thoroughly (W. Bleeker et al. 1999 and references therein). Nasturtium africanum Braun-Blanquet is known from Morocco in northwestern Africa.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Of conservation concern.
Nasturtium gambelii is known from southern California in Los Angeles, San Bernardino, San Luis Obispo, Santa Barbara, and Ventura counties. It is likely to be found also in undisturbed, freshwater habitats elsewhere in southern California and in Mexico and Central America. Intermediates between N. gambelii and N. officinale have been found in southern California, suggesting hybridization between them. Experimental work is needed to confirm this hypothesis.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Seeds biseriate, coarsely reticulate, with 25-50(-60) areolae on each side; fruits (1.8-) 2-2.5(-3) mm wide. | N. officinale |
1. Seeds uniseriate, minutely to moderately reticulate, with (75-)100-500 areolae on each side; fruits 0.8-1.2(-1.8) mm wide | → 2 |
2. Emergent leaves: petiolar bases non-auriculate; blades 3(-5)-foliolate; seeds light or yellowish brown; Florida. | N. floridanum |
2. Emergent leaves: petiolar bases often minutely auriculate; blades (3-)5-17-foliolate; seeds reddish brown; not Florida | → 3 |
3. Leaflet margins entire or repand; seeds with (75-)100-150(-175) areolae on each side; filaments 2.5-3.5 mm; petals 4.5-6 mm; petioles and rachises not winged. | N. microphyllum |
3. Leaflet margins coarsely dentate or, rarely, sinuate-repand; seeds with 300-450 areolae on each side; filaments 5-7 mm; petals 6-8 mm; petioles and rachises narrowly winged. | N. gambelii |
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