Flora of North America species comparison

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Draba arctogena

Draba pilosa

fellfield whitlowgrass
Habit Perennials; (cespitose); caudex branched (sometimes with persistent leaf remains); sometimes scapose. Perennials; (not stoloniferous); caudex branched (covered with persistent, dry leaves and midveins); scapose.
Stems

unbranched, 0.3–1.4 dm, pubescent throughout, trichomes simple, 0.2–1 mm, and 2–6-rayed, 0.05–0.3 mm.

unbranched, 0.4–1.7 dm, glabrous or pubescent, trichomes simple, 0.2–0.9 mm, and fewer, 2–4-rayed, 0.1–0.6 mm.
Basal leaves

rosulate;

petiolate;

petiole base and margin ciliate, (trichomes mostly simple, 0.2–1 mm);

blade oblanceolate to narrowly obovate, 0.4–1.7 cm × 1.5–6 mm, margins entire or with 1–3 teeth on each side, surfaces pubescent with primarily simple trichomes, 0.3–1mm, abaxially mixed with stalked, 4–10-rayed ones, 0.1–0.2 mm.

(imbricate); rosulate;

petiolate;

petiole (base thickened), ciliate throughout;

blade linear to linear-oblanceolate, 0.5–1.5(–2.2) cm × 1–2.5(–4) mm, margins entire (thickened, ciliate, trichomes simple and 2-rayed, to 1.1 mm), surfaces pubescent, abaxially with simple trichomes, 0.3–1 mm, and 2–4-rayed ones, 0.1–0.5 mm, adaxially similar, or with only simple trichomes, (midvein prominent, thickened).
Cauline leaves

0 or 1;

sessile;

blade ovate to oblong, margins entire or toothed, surfaces pubescent as basal.

0.
Racemes

2–14(–17)-flowered, ebracteate, elongated in fruit;

rachis not flexuous, pubescent as stem.

(2–)4–12-flowered, ebracteate, usually elongated in fruit;

rachis not flexuous, glabrous or pubescent as stem.
Flowers

sepals ovate, 1.8–2.5 mm, pubescent, (trichomes simple and short-stalked, 2–4-rayed);

petals white, spatulate, 3–4 × 1.5–2 mm;

anthers ovate, 0.3–0.4 mm.

sepals ovate, 2–3.5 mm, pubescent, (trichomes simple and short-stalked, 2-rayed);

petals pale to bright yellow, obovate, 3.5–6 × 2–3.5 mm;

anthers ovate, 0.4–0.5 mm.
Fruiting pedicels

suberect to ascending, straight, 1–5(–7) mm, pubescent, trichomes simple and 2–4-rayed.

divaricate-ascending, usually straight, rarely curved upward, 6–13 mm, glabrous or pubescent as stem.
Fruits

oblong, plane, flattened, 4–9 × 2–3.5 mm;

valves pubescent, trichomes short-stalked, 2–4-rayed, 0.1–0.5 mm, sometimes with simple ones;

ovules 20–32 per ovary;

style 0.1–0.4 mm (stigma distinctly wider than style).

elliptic to lanceolate, 5–11 × 3–4 mm, plane, flattened;

valves glabrous or puberulent with simple and short-stalked, 2-rayed trichomes, 0.07–0.3 mm;

ovules 12–20 per ovary;

style 0.4–0.9 mm (stigma about as wide as style).
Seeds

ovoid, 0.7–1 × 0.5–0.6 mm.

ovoid, 1.2–1.4 × 0.8–1 mm.
2n

= 48.

Draba arctogena

Draba pilosa
Phenology Flowering Jun–Jul. Flowering Jul–Aug.
Habitat Scree, sandy hills, gravel flats Dry gravelly slopes, sandy places, wet tundra
Elevation 0-450 m (0-1500 ft) 0-1300 m (0-4300 ft)
Distribution
from FNA
NT; NU; Greenland
[BONAP county map]
from FNA
AK; NT; NU; YT; e Asia (ne Russian Far East, n Siberia)
[BONAP county map]
Discussion

Draba arctogena is sometimes confused with D. norvegica, from which it differs by having less elongated fruiting racemes, abaxial leaf surfaces with 4–10-rayed (versus cruciform or, rarely, 2–6-rayed) trichomes, and fruits with 2–4-rayed trichomes, 0.1–0.5 mm, (versus glabrous or with simple and 2–4-rayed trichomes, 0.05–0.25 mm). The limits of D. arctica, D. arctogena, D. cinerea, and D. oblongata need to be critically evaluated in light of molecular and cytological data.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

O. E. Schulz (1927) reduced Draba pilosa to a variety of the decaploid D. alpina and cited North American collections. The former species was not listed by C. L. Hitchcock (1941) or R. C. Rollins (1993). From D. alpina, D. pilosa is easily distinguished by having strongly thickened and persistent (versus not thickened) midveins and margins, and usually narrower leaf blades [1–2.5(–5) versus 2.5–6(–9) mm wide].

As recognized herein, Draba pilosa is broadly circumscribed to include perhaps two or three closely related taxa. All are scapose plants with large, yellow flowers and prominent, persistent midveins and petioles. Some Alaskan forms (e.g., Parker 7596, ALA), which grow in moist heath habitats, have leaves 3–5 mm wide, whereas the majority have narrower leaf blades rarely reaching 2.5 mm in width. Most plants assigned to this species have leaves with exclusively simple trichomes and often glabrous scapes. Others (e.g., Chesemore & Davies 13, Murray 3371, Parker & Batten 8954, all at ALA) have leaf blade surfaces and scapes with 2–4-rayed trichomes and blade margins ciliate with simple trichomes. One collection (Walker s.n., ALA) has a mixture of plants of both trichome types but no intermediates were found. Detailed molecular and cytological studies are needed on this complex to determine if more than one taxon is represented.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 7, p. 292. FNA vol. 7, p. 330.
Parent taxa Brassicaceae > tribe Arabideae > Draba Brassicaceae > tribe Arabideae > Draba
Sibling taxa
D. abajoensis, D. albertina, D. aleutica, D. alpina, D. aprica, D. arabisans, D. arctica, D. argyrea, D. arida, D. asprella, D. asterophora, D. aurea, D. aureola, D. bifurcata, D. borealis, D. brachycarpa, D. brachystylis, D. breweri, D. burkei, D. californica, D. cana, D. carnosula, D. chamissonis, D. cinerea, D. corrugata, D. corymbosa, D. crassa, D. crassifolia, D. cruciata, D. cuneifolia, D. cusickii, D. cyclomorpha, D. daviesiae, D. densifolia, D. exunguiculata, D. fladnizensis, D. glabella, D. globosa, D. graminea, D. grandis, D. grayana, D. heilii, D. helleriana, D. hitchcockii, D. howellii, D. incana, D. incerta, D. incrassata, D. inexpectata, D. jaegeri, D. juvenilis, D. kassii, D. kluanei, D. lactea, D. lemmonii, D. lonchocarpa, D. longisquamosa, D. macounii, D. maguirei, D. malpighiacea, D. micropetala, D. mogollonica, D. monoensis, D. mulliganii, D. murrayi, D. nemorosa, D. nivalis, D. norvegica, D. novolympica, D. oblongata, D. ogilviensis, D. oligosperma, D. oreibata, D. oxycarpa, D. palanderiana, D. pauciflora, D. paucifructa, D. paysonii, D. pectinipila, D. pedicellata, D. pennellii, D. petrophila, D. pilosa, D. platycarpa, D. porsildii, D. praealta, D. pterosperma, D. ramosissima, D. ramulosa, D. rectifructa, D. reptans, D. ruaxes, D. santaquinensis, D. saxosa, D. scotteri, D. serpentina, D. sharsmithii, D. sibirica, D. sierrae, D. simmonsii, D. smithii, D. sobolifera, D. spectabilis, D. sphaerocarpa, D. sphaeroides, D. standleyi, D. stenoloba, D. stenopetala, D. streptobrachia, D. streptocarpa, D. subalpina, D. subcapitata, D. subumbellata, D. trichocarpa, D. ventosa, D. verna, D. viridis, D. weberi, D. yukonensis, D. zionensis
D. abajoensis, D. albertina, D. aleutica, D. alpina, D. aprica, D. arabisans, D. arctica, D. arctogena, D. argyrea, D. arida, D. asprella, D. asterophora, D. aurea, D. aureola, D. bifurcata, D. borealis, D. brachycarpa, D. brachystylis, D. breweri, D. burkei, D. californica, D. cana, D. carnosula, D. chamissonis, D. cinerea, D. corrugata, D. corymbosa, D. crassa, D. crassifolia, D. cruciata, D. cuneifolia, D. cusickii, D. cyclomorpha, D. daviesiae, D. densifolia, D. exunguiculata, D. fladnizensis, D. glabella, D. globosa, D. graminea, D. grandis, D. grayana, D. heilii, D. helleriana, D. hitchcockii, D. howellii, D. incana, D. incerta, D. incrassata, D. inexpectata, D. jaegeri, D. juvenilis, D. kassii, D. kluanei, D. lactea, D. lemmonii, D. lonchocarpa, D. longisquamosa, D. macounii, D. maguirei, D. malpighiacea, D. micropetala, D. mogollonica, D. monoensis, D. mulliganii, D. murrayi, D. nemorosa, D. nivalis, D. norvegica, D. novolympica, D. oblongata, D. ogilviensis, D. oligosperma, D. oreibata, D. oxycarpa, D. palanderiana, D. pauciflora, D. paucifructa, D. paysonii, D. pectinipila, D. pedicellata, D. pennellii, D. petrophila, D. platycarpa, D. porsildii, D. praealta, D. pterosperma, D. ramosissima, D. ramulosa, D. rectifructa, D. reptans, D. ruaxes, D. santaquinensis, D. saxosa, D. scotteri, D. serpentina, D. sharsmithii, D. sibirica, D. sierrae, D. simmonsii, D. smithii, D. sobolifera, D. spectabilis, D. sphaerocarpa, D. sphaeroides, D. standleyi, D. stenoloba, D. stenopetala, D. streptobrachia, D. streptocarpa, D. subalpina, D. subcapitata, D. subumbellata, D. trichocarpa, D. ventosa, D. verna, D. viridis, D. weberi, D. yukonensis, D. zionensis
Synonyms D. groenlandica var. arctogena, D. cinerea var. arctogena D. alpina var. pilosa, D. aspera
Name authority (E. Ekman) E. Ekman: Svensk Bot. Tidskr. 25: 492. (1932) Adams ex de Candolle: in A. P. de Candolle, Syst. Nat. 2: 336. (1821)
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Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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