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FNA | Family List | FNA Vol. 19, 20 and 21 | Asteraceae | Prenanthes

12. Prenanthes sagittata (A. Gray) A. Nelson in J. M. Coulter and A. Nelson, New Man. Bot. Centr. Rocky Mt. 592. 1909.

Arrowleaf snakeroot

Prenanthes alata (Hooker) D. Dietrich var. sagittata A. Gray in A. Gray et al., Syn. Fl. N. Amer. 1(2): 435. 1884; Nabalus sagittatus (A. Gray) Rydberg

Plants 8–75 cm; taproots short, thick and tuberous or long and slender, fascicled. Stems erect, greenish and mottled purplish, ± glabrous or proximally glabrate, distally glabrous. Leaves: proximal present at flowering; petiolate (petioles narrowly winged, sometimes lobed, 5–15 cm); blades ovate or deltate, 3–10 × 1.5–6 cm, thin, bases hastate to truncate or rounded, sometimes shallowly, palmately lobed, ultimate margins irregularly dentate, faces glabrous; distal reduced. Heads in narrow, elongate paniculiform or racemiform arrays. Calyculi 5–7, green, subulate to narrowly lanceolate bractlets 3–8 mm (longest 2/3 lengths of phyllaries), glabrous. Involucres narrowly campanulate (rounded), 7–13 × 5–8 mm. Phyllaries 7–12, green to tan, apices dark, linear-lanceolate, 8–12 mm, margins narrowly scarious, (apices sparsely ciliate), faces glabrous. Florets 10–19; corollas white, 9–15 mm. Cypselae brown, fusiform to oblance-oloid, subterete or angled, 5 mm, indistinctly 7–10-ribbed; pappi pale yellow, 5–6 mm. 2n = 16.

Flowering Jul–Aug. Stream banks, terraces, moist shady places, talus, rock crevices, mixed conifer woodlands; 1000–1600 m; Alta., B.C.; Idaho, Mont.

Prenanthes sagittata is similar to P. alata; it differs in its somewhat smaller stature, heads in narrower and more elongate arrays, and longer calyculi. The ranges of the two species do not overlap.


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