Flora of North America species comparison

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Arabis pycnocarpa var. adpressipilis

Arabis pycnocarpa var. pycnocarpa
Photo is of parent taxon
Photo is of parent taxon

blushing rock-cress, hairy fruit rock cress, hairy rockcress
Stems

pilose, trichomes appressed, malpighiaceous, or minutely stalked, forked, plants rarely glabrescent.

usually hirsute basally, rarely glabrescent, trichomes often simple, sometimes branched.
Basal leaves

blade surfaces pubescent, trichomes sessile, forked, and/or stellate.

blade surfaces sparsely to densely pubescent, trichomes simple and stalked.
Fruits

(4–)4.5–6(–6.5) cm;

style 0.5–1.3 mm.

(3.5–)4–5.8(–6) cm;

style (0.2–)0.5–1 mm, (rarely stout).
2n

= 32.

Arabis pycnocarpa var. adpressipilis

Arabis pycnocarpa var. pycnocarpa
Phenology Flowering Mar–Jun. Flowering Mar–Jul.
Habitat Ravines, pastures, cliffs, calcareous talus, dolomite glades, rich woods, bluffs, rocky ledges Bluffs, cliffs, ledges, rocky hillsides, open woods, bottom lands, gravel bars, meadows, streamsides, upland prairies, grassy swales, hillsides, stream bottoms
Elevation 0-300 m (0-1000 ft) 0-2500 m (0-8200 ft)
Distribution
from FNA
IA; IL; IN; KS; MO; NY; OH; PA; TN; VA; ON
[BONAP county map]
from FNA
AK; AZ; CA; CO; CT; IA; ID; KS; MA; ME; MI; MN; MT; ND; NE; NH; NJ; NM; NV; NY; OH; OR; PA; SD; UT; VA; VT; WI; WV; WY; AB; BC; LB; MB; NB; NS; NT; ON; QC; SK; YT; Asia (China, Japan, Russian Far East)
[BONAP county map]
Discussion

R. C. Rollins (1941, 1993) recognized both pycnocarpa and adpressipilis as distinct varieties of Arabis hirsuta; G. A. Mulligan (1996) treated adpressipilis as a synonym of A. hirsuta var. pycnocarpa. In my opinion, the differences in trichome morphology of the stems and leaves are significant enough to justify recognition of infraspecific taxa of one species.

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

Some populations in northern Indiana and northern Illinois, [e.g., Herman 8790 (Jo Davies County) and Friesner 19072 (Elkhart County), both at GH] most likely represent hybrids between the two varieties of Arabis pycnocarpa. Trichomes borne proximally on stems of these plants are a mixture of forked and simple. It is expected that hybrids can be found where the ranges of the two taxa overlap.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 7, p. 260. FNA vol. 7, p. 260.
Parent taxa Brassicaceae > tribe Arabideae > Arabis > Arabis pycnocarpa Brassicaceae > tribe Arabideae > Arabis > Arabis pycnocarpa
Sibling taxa
A. pycnocarpa var. pycnocarpa
A. pycnocarpa var. adpressipilis
Synonyms A. hirsuta var. adpressipilis A. hirsuta var. minshallii, A. pycnocarpa var. reducta
Name authority M. Hopkins: Rhodora 39: 117. (1937) unknown
Web links 
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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