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collin's suncress, Collins' rockcress

Habit Perennials; usually short-lived; sexual; caudex not woody. Perennials; short-lived; apomictic; caudex usually not woody.
Stems

usually 1 per caudex branch, arising from center of rosette near ground surface, (1.5–)2.5–8 dm, densely pubescent proximally, trichomes simple and short-stalked, 2-rayed, to 1 mm, sparsely pubescent or glabrous distally.

3 to many per caudex branch, arising from margin of rosette near ground surface, 3.5–6 dm, pubescent proximally, trichomes short-stalked, 2–4-rayed, 0.2–0.3 mm, glabrous distally.

Basal leaves

blade oblanceolate, 1–7 mm wide, margins entire or dentate, ciliate along petiole, trichomes (simple), to 0.7 mm, surfaces moderately to densely pubescent, trichomes short-stalked, 5–8-rayed, 0.15–0.4 mm.

blade oblanceolate, 3–7 mm wide, margins dentate, ciliate proximally, trichomes (simple), to 0.3 mm, surfaces pubescent, trichomes short-stalked, 4–8-rayed, 0.05–0.2 mm.

Cauline leaves

(8–)15–40, concealing stem proximally;

blade auricles 1–3 mm, surfaces of distalmost leaves usually sparsely pubescent.

5–10, not concealing stem;

blade auricles 0.5–1 mm, surfaces of distalmost leaves glabrous.

Racemes

(15–)30–90-flowered, usually unbranched.

10–18-flowered, usually unbranched.

Flowers

descending to pendent at anthesis;

sepals pubescent;

petals usually white, rarely lavender, 4–6 × 0.8–1.5 mm, glabrous;

pollen ellipsoid.

divaricate-ascending at anthesis;

sepals pubescent;

petals lavender, 4–6 × 1–1.5 mm, glabrous;

pollen spheroid.

Fruiting pedicels

reflexed, abruptly recurved at base, otherwise straight, 4–13 mm, glabrous or sparsely pubescent, trichomes usually simple.

divaricate-descending, straight, 5–10 mm, glabrous.

Fruits

strongly reflexed, usually appressed to rachis, rarely somewhat secund, straight, edges parallel, 3.5–6 cm × 0.9–1.5 mm;

valves glabrous;

ovules 70–126 per ovary;

style 0.2–0.5 mm.

divaricate-descending, not appressed to rachis, not secund, curved, edges parallel, 4–6 cm × 1.5–1.8 mm;

valves glabrous;

ovules 60–70 per ovary;

style 0.1–0.4 mm.

Seeds

uniseriate, 1–1.4 × 0.8–1 mm;

wing continuous (rarely absent), to 0.1 mm wide.

uniseriate, 1.5–2 × 1–1.3 mm;

wing distal, ca. 0.1 mm wide.

2n

= 14.

Boechera collinsii

Boechera fructicosa

Phenology Flowering May–Jun. Flowering Jun–Jul.
Habitat Rocky and gravelly hillsides, prairies, open woods, floodplains Dry, disturbed soil
Elevation 600-1400 m (2000-4600 ft) ca. 2000 m (ca. 6600 ft)
Distribution
from FNA
ID; MN; MT; ND; NE; SD; WY; AB; MB; QC; SK
[WildflowerSearch map]
[BONAP county map]
from FNA
WY
[BONAP county map]
Discussion

Though often treated as a variety of Arabis (Boechera) holboellii (e.g., R. C. Rollins 1993; G. A. Mulligan 1996), B. collinsii is easily distinguished from that species by having simple and 2-rayed (versus 4–8-rayed) trichomes proximally on stems, and narrower (0.9–1.5 versus 2–2.5 mm) usually non-secund fruits. The two taxa also show allopatric distributions, with B. collinsii found on the North American continent (usually east of the Rocky Mountains) and B. holboellii apparently confined to Greenland.

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

Boechera fructicosa is known only from the type collection (A. & E. Nelson 5681) taken near Undine Falls in Park County. Multiple plants are represented (comprising the holotype and four isotypes), though one specimen with the same number at RM is B. stricta. Although the exact parentage of this apomictic hybrid remains in doubt, it is virtually certain that B. microphylla contributed at least one genome.

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

Source FNA vol. 7, p. 370. FNA vol. 7, p. 379.
Parent taxa Brassicaceae > tribe Boechereae > Boechera Brassicaceae > tribe Boechereae > Boechera
Sibling taxa
B. acutina, B. arcuata, B. atrorubens, B. bodiensis, B. breweri, B. burkii, B. calderi, B. californica, B. canadensis, B. cascadensis, B. cobrensis, B. consanguinea, B. constancei, B. covillei, B. crandallii, B. cusickii, B. davidsonii, B. dentata, B. depauperata, B. dispar, B. divaricarpa, B. drepanoloba, B. duchesnensis, B. elkoensis, B. evadens, B. falcatoria, B. falcifructa, B. fecunda, B. fendleri, B. fernaldiana, B. formosa, B. fructicosa, B. glareosa, B. glaucovalvula, B. goodrichii, B. gracilenta, B. gracilipes, B. grahamii, B. gunnisoniana, B. harrisonii, B. hastatula, B. hoffmannii, B. holboellii, B. horizontalis, B. howellii, B. inyoensis, B. johnstonii, B. koehleri, B. laevigata, B. languida, B. lasiocarpa, B. lemmonii, B. lignifera, B. lincolnensis, B. lyallii, B. macounii, B. microphylla, B. missouriensis, B. nevadensis, B. ophira, B. oxylobula, B. paddoensis, B. pallidifolia, B. parishii, B. pauciflora, B. paupercula, B. peirsonii, B. pendulina, B. pendulocarpa, B. perennans, B. perstellata, B. pinetorum, B. pinzliae, B. platysperma, B. polyantha, B. porphyrea, B. pratincola, B. puberula, B. pulchra, B. pusilla, B. pygmaea, B. quebecensis, B. rectissima, B. repanda, B. retrofracta, B. rigidissima, B. rollei, B. rollinsiorum, B. rubicundula, B. saximontana, B. schistacea, B. serotina, B. serpenticola, B. shevockii, B. shockleyi, B. sparsiflora, B. spatifolia, B. stricta, B. subpinnatifida, B. suffrutescens, B. texana, B. tiehmii, B. tularensis, B. ultra-alsa, B. villosa, B. williamsii, B. xylopoda, B. yorkii
B. acutina, B. arcuata, B. atrorubens, B. bodiensis, B. breweri, B. burkii, B. calderi, B. californica, B. canadensis, B. cascadensis, B. cobrensis, B. collinsii, B. consanguinea, B. constancei, B. covillei, B. crandallii, B. cusickii, B. davidsonii, B. dentata, B. depauperata, B. dispar, B. divaricarpa, B. drepanoloba, B. duchesnensis, B. elkoensis, B. evadens, B. falcatoria, B. falcifructa, B. fecunda, B. fendleri, B. fernaldiana, B. formosa, B. glareosa, B. glaucovalvula, B. goodrichii, B. gracilenta, B. gracilipes, B. grahamii, B. gunnisoniana, B. harrisonii, B. hastatula, B. hoffmannii, B. holboellii, B. horizontalis, B. howellii, B. inyoensis, B. johnstonii, B. koehleri, B. laevigata, B. languida, B. lasiocarpa, B. lemmonii, B. lignifera, B. lincolnensis, B. lyallii, B. macounii, B. microphylla, B. missouriensis, B. nevadensis, B. ophira, B. oxylobula, B. paddoensis, B. pallidifolia, B. parishii, B. pauciflora, B. paupercula, B. peirsonii, B. pendulina, B. pendulocarpa, B. perennans, B. perstellata, B. pinetorum, B. pinzliae, B. platysperma, B. polyantha, B. porphyrea, B. pratincola, B. puberula, B. pulchra, B. pusilla, B. pygmaea, B. quebecensis, B. rectissima, B. repanda, B. retrofracta, B. rigidissima, B. rollei, B. rollinsiorum, B. rubicundula, B. saximontana, B. schistacea, B. serotina, B. serpenticola, B. shevockii, B. shockleyi, B. sparsiflora, B. spatifolia, B. stricta, B. subpinnatifida, B. suffrutescens, B. texana, B. tiehmii, B. tularensis, B. ultra-alsa, B. villosa, B. williamsii, B. xylopoda, B. yorkii
Synonyms Arabis collinsii, Arabis holboellii var. collinsii, Arabis retrofracta var. collinsii Arabis fructicosa
Name authority (Fernald) Á. Löve & D. Löve: Taxon 31: 125. (1982) (A. Nelson) Al-Shehbaz: Novon 13: 385. (2003)
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