A primary distinction between the four species of thicket-forming roses in California involves the prickles (technically not thorns, which would be anatomically different structures). Prickles are best observed on middle and upper parts of the stem (i.e., the parts typically represented on herbarium specimens); prickles at the base of the plant are often significantly denser, straighter, thicker, and/or otherwise morphologically dissimilar to those on middle and upper parts of the plant. They can furthermore differ on different stems of the same plant, for reasons not yet understood.
|CALIFORNICA||NUTKANA var. NUTKANA||PISOCARPA||WOODSII var. ULTRAMONTANA|
|PRICKLES||strongly curved, thick-based (image)||+/- straight, very thick, abundant (image)||+/- straight, paired or nearly absent (image)||straight or ± curved, gen slender, few to many (image)|
|PEDICELS||hairy but not glandular||glabrous or glandular||gen glabrous, glandless||gen glabrous, glandless|
|HIPS||ovoid, glabrous to hairy (image)||large, round or ovoid, glabrous or stalked-glandular (image)||round, glabrous (image)||ovoid, glabrous (image)|
|SEPALS||glandular or not, tip = body, entire||gen glandular, tip expanded, toothed||gen glandular, tip > body, entire||glandless, tip = body, entire|
|DISTRIBUTION||south & central cismontane CA, sw Oregon, n Baja California (map)||near coast in central CA, north to Alaska (map)||northwest CA to Brit. Columbia (map)||transmontane CA to Montana and Brit. Columbia (map)|
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