Lepidium densiflorum |
Lepidium fremontii |
|
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baby-seed pepper-weed, common pepper-grass, common pepper-weed, elongate peppergrass, hairy-fruit peppergrass, large-fruit peppergrass, miner's pepper-weed, prairie pepper-grass, prairie pepperweed |
desert pepper grass, desert pepperweed |
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Habit | Annuals or biennials; puberulent or glabrous, (trichomes cylindrical). | Perennials or subshrubs; (woody base aboveground); (glaucous), glabrous throughout. |
Stems | simple from base, erect, branched distally, (1–)2.5–5(–6.5) dm. |
several from base, erect or ascending, branched (several) distally, 2–5.5(–10) dm. |
Basal leaves | (early withered); rosulate; petiole 0.5–1.5(–2) cm; blade oblanceolate, spatulate, or oblong, (1.5–)2.5–8(–11) cm × 5–10(–20) mm, margins coarsely serrate or pinnatifid. |
absent. |
Cauline leaves | shortly petiolate; blade narrowly oblanceolate or linear, (0.7–)1.3–6.2(–8) cm × (0.5–)1.5–10(–18) mm, base attenuate to cuneate, not auriculate, margins usually entire or irregularly serrate to dentate, rarely pinnatifid. |
sessile; blade linear and undivided or pinnately lobed (lobes 3–7(–9), linear), (1.5–)2.2–8.4(–10.2) cm × (0.7–)1–2.8(–4.2) mm, base attenuate, not auriculate, margins entire, (similar, smaller distally). |
Racemes | considerably elongated in fruit; rachis puberulent, trichomes straight, slender to subclavate. |
(panicles), elongated in fruit. |
Flowers | sepals oblong, 0.5–0.8(–1) × 0.3–0.5 mm; petals (absent or rudimentary) white, filiform, 0.3–0.9 mm, claw absent; stamens 2, median; filaments 0.6–1(–1.8) mm; anthers 0.1–0.2 mm. |
sepals obovate, 1.5–2.5(–3) × 1–1.6 mm; petals white, spatulate, 2.5–4.2 × 1.5–2.2 mm, claw 1–2 mm; stamens 6; filaments 1.8–3 mm; anthers 0.4–0.7 mm. |
Fruiting pedicels | divaricate-ascending to horizontal, straight or slightly recurved, (terete), (1.5–)2–3.5(–4) × 0.15–0.25 mm, puberulent adaxially. |
divaricate-ascending to horizontal, usually straight, rarely slightly curved, (terete), (3.5–)4.3–7.6(–8.5) × 0.15–0.2 mm. |
Fruits | obovate to obovate-suborbicular, (2–)2.5–3(–3.5) × 1.5–2.5(–3) mm (widest beyond middle), apically winged, apical notch 0.2–0.4 mm deep; valves thin, smooth, not veined, glabrous or sparsely puberulent (at least on margin); style 0.1–0.2 mm, included in apical notch. |
obovate to orbicular, (4–)4.5–7(–8) × 4.2–7(–8) mm, apically winged, apical notch (0.1–)0.2–0.5 mm deep; valves thin, smooth, not veined; style 0.2–0.8(–1) mm, exserted beyond apical notch. |
Seeds | ovate, 1.1–1.3(–1.5) × 0.8–0.9 mm. |
ovate, 1.6–2.1 × 0.9–1.1 mm. |
2n | = 32. |
= 32. |
Lepidium densiflorum |
Lepidium fremontii |
|
Phenology | Flowering May–Jul. | Flowering Mar–Jun. |
Habitat | Waste places, disturbed sites, prairies, fields, pastures, grasslands, chaparral, meadows, sagebrush flats, flood plains, gravelly hillsides, rock crevices, seashores, sandy places, shaley barrens, open mesa, roadsides | Desert shrub communities, pinyon-juniper woodlands, sandy washes, gravelly deserts, barren knolls, bluffs, roadsides, steep limestone outcrops, rocky ledges and slopes |
Elevation | 0-3500 m (0-11500 ft) | 400-2100 m (1300-6900 ft) |
Distribution |
AK; AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NL; NS; NT; ON; PE; QC; SK; YT; Mexico (Chihuahua, Nuevo León) [Introduced in Europe, Asia]
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AZ; CA; NV; UT
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Discussion | North American records of Lepidium apetalum Willdenow mostly represent misidentifications of L. densiflorum. The latter has obovate fruits widest beyond the middle, whereas L. apetalum has elliptic fruits widest at the middle. The number and limits of the varieties recognized in Lepidium densiflorum, as well as the characters used to delimit them, vary among authors (A. Thellung 1906; C. L. Hitchcock 1936; G. A. Mulligan 1961; R. C. Rollins 1993; N. H. Holmgren 2005b). The variation almost always does not correlate with geography, and the recognition of varieties in this species is neither practical nor very useful. All of those authors admitted that these varieties are “very weak at best” (Rollins, p. 554). Of them, perhaps var. pubicarpum (including var. elongatum) might merit recognition. It is distributed in almost all of the Mountain and Pacific states and is distinguished from the other varieties solely by the presence of trichomes or minute papillae on the fruit valves. The density of these trichomes ranges from moderate and covering the entire valve surface to very sparse and represented by individual papillate trichomes restricted to the valve margin. Furthermore, the length of these trichomes may vary from ca. 0.01 to 0.3 mm. In some species (e.g., L. dictyotum) both glabrous- and pubescent-fruited forms occur, yet none of the above authors gave formal recognition to both forms. It is not known if both glabrous and puberulent fruits occur within the same population in L. densiflorum. The species is autogamous, but nothing is known about the rates of gene flow between and within populations. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Rollins established var. stipitatum on the basis of fruits obovate with gynophores 0.5–0.75 mm versus (var. fremontii) fruits orbicular to ovate and sessile. These two characters often do not covary and stipitate fruits occur sporadically throughout the species range, including Arizona (Lemmon s.n., GH), California (Morefield 3427, GH), and Nevada (Comanor 18, GH; Hitchcock 3078, GH). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 7, p. 579. | FNA vol. 7, p. 582. |
Parent taxa | Brassicaceae > tribe Lepidieae > Lepidium | Brassicaceae > tribe Lepidieae > Lepidium |
Sibling taxa | ||
Synonyms | L. densiflorum var. elongatum, L. densiflorum var. macrocarpum, L. densiflorum var. pubicarpum, L. densiflorum var. ramosum, L. elongatum, L. neglectum, L. pubicarpum, L. ramosum | L. fremontii var. stipitatum, Nasturtium fremontii |
Name authority | Schrader: Index Seminum (Göttingen) 1832: 4. (1832) | S. Watson: Botany (Fortieth Parallel), 30, plate 4, figs. 3, 4. (1871) |
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