Arabis modesta

Rollins

Rhodora 43: 350. 1941.

Endemic
Treatment appears in FNA Volume 7. Treatment on page 264. Mentioned on page 258.

Perennials; (caudex usually simple, rarely branched, covered with persistent petiolar remains); sparsely to densely pubescent, trichomes short-stalked, cruciform, or 3-rayed stellate, (0.3–0.5 mm). Stems simple or few from base (caudex), erect, usually unbranched, rarely branched (few) distally, 2.2–5.5 (–6.7) dm, (usually pubescent throughout, rarely subglabrate distally, trichomes stellate). Basal leaves: petiole 1–4 (–5) cm, (rarely minutely ciliate near base); blade oblanceolate to obovate, (0.8–) 2–4.5 (–6) cm × (4–) 10–20 (–25) mm, margins entire, repand, or dentate, (not ciliate), apex obtuse, surfaces pubescent, trichomes short-stalked, stellate. Cauline leaves (2–) 4–6 (–9); blade oblong or ovate, 1–3.5 (–4.5) cm × (3–) 6–10 (–20) mm, base not auriculate, margins entire, repand, or dentate, apex obtuse or acute, surfaces pubescent, trichomes short-stalked, stellate. Racemes simple, (dense). Fruiting pedicels ascending to divaricate, 7–18 (–25) mm. Flowers: sepals (purple), oblong, (4–) 5–6.5 (–8) × 1.5–2 mm, lateral pair saccate basally; petals purple, spatulate, (10–) 12–16 (–20) × 4–6 (–7) mm, apex rounded; filaments (4–) 5–8 mm; anthers narrowly oblong, 1.3–2 mm. Fruits suberect to divaricate, sometimes slightly curved, slightly torulose, (2.8–) 3.5–6 cm × 1.5–2 mm; valves each with prominent midvein extending to middle or full length; ovules 20–34 per ovary; style 0.5–1 (–1.5) mm. Seeds winged distally, oblong, 1.7–2.2 × 0.9–1.2 mm; wing 0.2–0.5 mm wide. 2n = 32.


Phenology: Flowering Mar–Apr(-May).
Habitat: Moist shaded banks, slopes, rocky canyon walls, talus, basaltic bluffs
Elevation: 150-500 m

Discussion

Arabis modesta, known only from Napa, Siskiyou, and Yolo counties (California), and Jackson and Josephine counties (Oregon), and the following four species form a well-defined group easily separated from the first nine species above by their large, purple petals. Arabis modesta is readily distinguished from other purple-flowered Arabis by having very fine, short-stalked cruciform and 3-rayed, instead of simple and 2-rayed, forked trichomes. Arabis blepharophylla has broadly winged, orbicular seeds, and the other purple-flowered species (A. aculeolata, A. mcdonaldiana, A. oregana) have oblong seeds that are not winged or narrowly winged distally. The lines separating these three species are not as well-defined as those of A. blepharophylla and A. modesta, and further studies are needed to resolve them. I prefer to maintain all five species of purple-flowered Arabis as distinct until thorough molecular and hybridization studies are conducted. In the absence of such studies, it is unwise to make any nomenclatural changes.

Selected References

None.

Lower Taxa

None.

"elongated" is not a number."thick" is not a number."dm" is not declared as a valid unit of measurement for this property."dm" is not declared as a valid unit of measurement for this property.

... more about "Arabis modesta"
0.13 cm1.3 mm <br />0.0013 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
rounded +, acute +  and obtuse +
Ihsan A. Al-Shehbaz +
Rollins +
sessile +  and petiolate +
not auriculate +
appendaged +  and unappendaged +
3.5 cm35 mm <br />0.035 m <br /> (4.5 cm45 mm <br />0.045 m <br />) +
1 cm10 mm <br />0.01 m <br /> (2 cm20 mm <br />0.02 m <br />) +
not +  and auriculate +
1 cm10 mm <br />0.01 m <br /> (3.5 cm35 mm <br />0.035 m <br />) +
lyrate-pinnatifid +, dentate to denticulate +  and entire +
dissected +, repand +, sinuate +, crenate +  and dentate +
ovate;oblong;oblanceolate;obovate +
much smaller +  and reduced +
0.6 cm6 mm <br />0.006 m <br /> (1 cm10 mm <br />0.01 m <br />) +
urceolate +, campanulate +  and tubular +
branched +  and simple +
petiolate +  and sessile +
well-developed +
distinct +
differentiated +
emarginate +  and entire +
Calif. +  and Oreg. +
150-500 m +
straight +  and curved +
not winged +  and unappendaged +
0.4 cm4 mm <br />0.004 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
connate +  and distinct +
0.5 cm5 mm <br />0.005 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
actinomorphic +
0.65 cm6.5 mm <br />0.0065 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
0.5 cm5 mm <br />0.005 m <br /> (0.65 cm6.5 mm <br />0.0065 m <br />) +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
latiseptate +  and unsegmented +
2.8 cm28 mm <br />0.028 m <br /> (3.5 cm35 mm <br />0.035 m <br />) +
indehiscent +  and dehiscent +
3.5 cm35 mm <br />0.035 m <br /> (6 cm60 mm <br />0.06 m <br />) +
torulose +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
latiseptate +, stipitate +  and sessile +
flattened +  and torulose +
Moist shaded banks, slopes, rocky canyon walls, talus, basaltic bluffs +
annular +  and semiannular +
sessile +  and petiolate +
alternate +, not +  and rosulate +
cauline +  and basal +
connate +  and distinct +
decurrent +
dentate +  and entire +
dentate;repand;dentate;repand;entire;dentate;repand;dentate;repand;entire +
forked +
tenuinucellate +, crassinucellate +  and bitegmic +
campylotropous +  and anatropous +
1.6 cm16 mm <br />0.016 m <br /> (2 cm20 mm <br />0.02 m <br />) +
0.6 cm6 mm <br />0.006 m <br /> (0.7 cm7 mm <br />0.007 m <br />) +
purple +, pink +  and white +
12mm;16mm +
rudimentary +
spatulate +
0.4 cm4 mm <br />0.004 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
4 cm40 mm <br />0.04 m <br /> (5 cm50 mm <br />0.05 m <br />) +
1 cm10 mm <br />0.01 m <br /> (4 cm40 mm <br />0.04 m <br />) +
Flowering Mar–Apr(-May). +
trinucleate +  and 3(-11)-colpate +
1.8 cm18 mm <br />0.018 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
slender +
0.7 cm7 mm <br />0.007 m <br /> (1.8 cm18 mm <br />0.018 m <br />) +
mucilaginous +
uniseriate +  and biseriate +
not +  and mucilaginous +
white +, black +, brown +  and yellow +
0.17 cm1.7 mm <br />0.0017 m <br /> (0.22 cm2.2 mm <br />0.0022 m <br />) +
0.09 cm0.9 mm <br />9.0e-4 m <br /> (0.12 cm1.2 mm <br />0.0012 m <br />) +
not basally +  and saccate +
persistent +  and caducous +
distinct +
ascending +  and erect +
oblong +  and ovate +
reduced +
latiseptate +  and unsegmented +
indehiscent +  and dehiscent +
latiseptate +  and unsegmented +
indehiscent +  and dehiscent +
tetradynamous +
branched +, unbranched +  and simple +
procumbent +  and decumbent +
subsessile +, sessile +  and petiolate +
0.1 cm1 mm <br />0.001 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
persistent +
distinct +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
Cruciferae +
Arabis modesta +
species +
cruciform +
coiled +, 1-7-veined +  and veined +
anastomosing +
rhizomatous +, taprooted +, scapose +  and not +
perennial +, biennial +  and annual +
subshrub +  and herb +
aquatics +  and terrestrial +
glabrous +  and pubescent +
0.2mm;0.5mm +