Arabis pycnocarpa

M. Hopkins

Rhodora 39: 112, plate 458, figs. 1–3. 1937.

Synonyms: Arabis hirsuta subsp. pycnocarpa (M. Hopkins) Hultén Arabis hirsuta var. pycnocarpa (M. Hopkins) Rollins
Treatment appears in FNA Volume 7. Treatment on page 259. Mentioned on page 258, 260, 261, 262.

Biennials or perennials; (caudex branched); usually densely hirsute (at least basally), rarely glabrescent, trichomes simple mixed with stalked or sessile, forked ones. Stems simple or several from base (rosette), erect, often branched distally, 1–8 dm, (pilose with trichomes appressed, malpighiaceous, or minutely stalked, forked, or hirsute basally with trichomes simple and minutely stalked, forked, sometimes almost exclusively pubescent with forked submalpighiaceous trichomes). Basal leaves: petiole 0.5–2 cm, (ciliate or not); blade spatulate, oblanceolate, or oblong, (0.8–) 1.5–8 cm × (5–) 10–25 mm, margins entire, repand, or dentate, apex obtuse or acute, surfaces sparsely to densely pubescent, trichomes sessile or stalked, simple or forked, and/or stellate. Cauline leaves (7–) 10–45 (–61), (overlapping or not); blade ovate to oblong or lanceolate, rarely linear, (1–) 1.5–6 (–8) cm × (1–) 3–20 (–25) mm, base subcordate or auriculate (auricles obtuse or subacute), margins dentate or entire, apex acute or obtuse, surfaces hirsute or adaxially glabrescent. Racemes often simple. Fruiting pedicels erect to erect-ascending, (2–) 3–8 (–12) mm (glabrous or sparsely pubescent). Flowers: sepals oblong, 2.5–4 × 0.5–1.5 mm, lateral pair not saccate basally; petals white, linear-oblanceolate or narrowly spatulate, 3.5–5 (–5.5) × 1–2 (–2.5) mm, apex obtuse; filaments 2.5–4 mm; anthers oblong, 0.7–1 mm. Fruits erect to erect-ascending, (often appressed to rachis), torulose, (3.5–) 4–6 (–6.5) cm × 0.8–1 (–1.2) mm; valves each with obscure or somewhat prominent midvein extending to the middle; ovules (54–) 60–86 per ovary; style (0.2–) 0.5–1 (–1.3) mm, (slender). Seeds narrowly winged throughout, oblong or suborbicular, (0.8–) 1–1.5 (–1.7) × 0.8–1.3 mm; wing to 0.2 mm wide distally.

Distribution

V7 341-distribution-map.gif

Alta., B.C., Man., N.B., N.S., N.W.T., Nfld. and Labr., Ont., Que., Sask., Yukon, Alaska, Ariz., Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Kans., Maine, Mass., Mich., Minn., Mo., Mont., N.Dak., N.H., N.J., N.Mex., N.Y., Nebr., Nev., Ohio, Oreg., Pa., S.Dak., Tenn., Utah, Va., Vt., W.Va., Wis., Wyo., Asia

Discussion

Varieties 2 (2 in the flora).

M. Hopkins (1937) synthesized earlier works on Arabis pycnocarpa and concluded that it is different from the European A. hirsuta. Both R. C. Rollins (1941, 1993) and G. A. Mulligan (1996) considered the North American and European plants different varieties of A. hirsuta; Mulligan recognized var. hirsuta in North America and Rollins did not. After examining thousands of specimens from Europe, Asia, and North America, I conclude that Hopkins was correct in treating the North American plants as a different species, A. pycnocarpa. The European A. hirsuta is a diploid (2n = 16) that has fruits 1.5–4 cm, stout styles 0.1–0.5 mm, prominent midvein extending the full length of the fruit valve, and 30–40(–44) ovules/seeds per ovary/fruit. By contrast, A. pycnocarpa is a tetraploid (2n = 32) that has fruits (3.5–)4–6(–6.5) cm, often slender styles (0.2–)0.5–1(–1.3) mm, obscure midvein hardly extending to the middle of the fruit valve, and ovules/seeds (54–)60–86 per ovary/fruit. Hopkins listed other differences in the number of cauline leaves and the development of seed wing, but these do not hold. Mulligan treated the perennial North American plants with minute styles as var. hirsuta and the biennial ones with longer styles as var. pycnocarpa. Habit and style length are not correlated at all, and one finds both biennials and perennials flowering in the same population.

Selected References

None.

Key

1 Stems usually hirsute basally, rarely glabrescent, trichomes often simple, sometimes branched; basal leaf blades: surfaces with simple and stalked trichomes. Arabis pycnocarpa var. pycnocarpa
1 Stems pilose, trichomes appressed, malpighiaceous, or minutely stalked, forked; basal leaf blades: surfaces with sessile, forked, and/or stellatetrichomes. Arabis pycnocarpa var. adpressipilis

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

... more about "Arabis pycnocarpa"
0.07 cm0.7 mm <br />7.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
Obtuse (?) +  and Acute (?) +
Ihsan A. Al-Shehbaz +
M. Hopkins +
sessile +  and petiolate +
auriculate +  and subcordate +
appendaged +  and unappendaged +
6 cm60 mm <br />0.06 m <br /> (8 cm80 mm <br />0.08 m <br />) +
2 cm20 mm <br />0.02 m <br /> (2.5 cm25 mm <br />0.025 m <br />) +
1.5 cm15 mm <br />0.015 m <br /> (6 cm60 mm <br />0.06 m <br />) +
lyrate-pinnatifid +, dentate to denticulate +  and entire +
dissected +, repand +, sinuate +, crenate +  and dentate +
ovate;oblong or lanceolate +
much smaller +  and reduced +
3mm;20mm +
urceolate +, campanulate +  and tubular +
branched +  and simple +
petiolate +  and sessile +
well-developed +
distinct +
differentiated +
emarginate +  and entire +
Alta. +, B.C. +, Man. +, N.B. +, N.S. +, N.W.T. +, Nfld. and Labr. +, Ont. +, Que. +, Sask. +, Yukon +, Alaska +, Ariz. +, Calif. +, Colo. +, Conn. +, Idaho +, Ill. +, Ind. +, Iowa +, Kans. +, Maine +, Mass. +, Mich. +, Minn. +, Mo. +, Mont. +, N.Dak. +, N.H. +, N.J. +, N.Mex. +, N.Y. +, Nebr. +, Nev. +, Ohio +, Oreg. +, Pa. +, S.Dak. +, Tenn. +, Utah +, Va. +, Vt. +, W.Va. +, Wis. +, Wyo. +  and Asia +
straight +  and curved +
not winged +  and unappendaged +
connate +  and distinct +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
actinomorphic +
latiseptate +  and unsegmented +
6 cm60 mm <br />0.06 m <br /> (6.5 cm65 mm <br />0.065 m <br />) +
0.1 cm1 mm <br />0.001 m <br /> (0.12 cm1.2 mm <br />0.0012 m <br />) +
indehiscent +  and dehiscent +
erect +  and erect-ascending +
torulose +
0.08 cm0.8 mm <br />8.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
latiseptate +, stipitate +  and sessile +
flattened +  and torulose +
annular +  and semiannular +
sessile +  and petiolate +
alternate +, not +  and rosulate +
cauline +  and basal +
connate +  and distinct +
decurrent +
entire +  and dentate +
dentate;repand;dentate;repand;entire +
prominent +  and obscure +
sessile +  and stalked +
forked +
tenuinucellate +, crassinucellate +  and bitegmic +
campylotropous +  and anatropous +
0.5 cm5 mm <br />0.005 m <br /> (0.55 cm5.5 mm <br />0.0055 m <br />) +
0.2 cm2 mm <br />0.002 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
0.35 cm3.5 mm <br />0.0035 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
rudimentary +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
0.5 cm5 mm <br />0.005 m <br /> (2 cm20 mm <br />0.02 m <br />) +
trinucleate +  and 3(-11)-colpate +
0.8 cm8 mm <br />0.008 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
elongated +
erect +  and erect-ascending +
slender +
0.3 cm3 mm <br />0.003 m <br /> (0.8 cm8 mm <br />0.008 m <br />) +
mucilaginous +
uniseriate +  and biseriate +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.17 cm1.7 mm <br />0.0017 m <br />) +
not +  and mucilaginous +
White (?) +, Black (?) +, Brown (?) +  and Yellow (?) +
0.1 cm1 mm <br />0.001 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
suborbicular +  and oblong +
0.08 cm0.8 mm <br />8.0e-4 m <br /> (0.13 cm1.3 mm <br />0.0013 m <br />) +
persistent +  and caducous +
distinct +
ascending +  and erect +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
reduced +
latiseptate +  and unsegmented +
indehiscent +  and dehiscent +
latiseptate +  and unsegmented +
indehiscent +  and dehiscent +
tetradynamous +
branched +  and simple +
procumbent +  and decumbent +
subsessile +, sessile +  and petiolate +
0.1 cm1 mm <br />0.001 m <br /> (0.13 cm1.3 mm <br />0.0013 m <br />) +
persistent +
distinct +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
glabrescent +, hirsute +  and pubescent +
Arabis hirsuta subsp. pycnocarpa +  and Arabis hirsuta var. pycnocarpa +
Arabis pycnocarpa +
species +
forked and/or stellate +, simple +, stalked +  and sessile +
stellate +  and forked +
coiled +, 1-7-veined +  and veined +
anastomosing +
perennial +  and biennial +
hirsute +  and glabrescent +
rhizomatous +, taprooted +, scapose +  and not +
perennial +, biennial +  and annual +
subshrub +  and herb +
aquatics +  and terrestrial +
glabrous +  and pubescent +
0mm;0.2mm +