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FNA | Family List | FNA Vol. 20 | Asteraceae | Isocoma

1. Isocoma acradenia (Greene) Greene, Erythea. 2: 111. 1894.

Alkali jimmyweed

Bigelowia acradenia Greene, Bull. Torrey Bot. Club 10: 126. 1883 (as Bigelovia); Haplopappus acradenius (Greene) S. F. Blake

Herbage usually glabrous, sometimes minutely hispidulous, often stipitate-glandular, often resinous. Leaf blades oblanceolate to narrowly obovate, 20–150 mm, margins entire or toothed or lobed (teeth or lobes apically rounded-obtuse). Involucres 5–8 × 5–7 mm. Phyllary apices yellowish to greenish yellow, sometimes spinulose-aristate, usually not gland-dotted, usually with single, strongly developed, subepidermal resin pocket nearly as wide as bracts, sometimes a central pocket and 2+ smaller, lateral ones (resin pockets sometimes formed from numerous, coalesced, sessile glands). Florets 12–27; corollas 5–7(–8) mm. Cypsela ribs not forming apical horns.

Isocoma acradenia is distinctive in its whitish stems and narrow, whitish-indurate phyllaries with an apical resin pocket (or pockets). The leaves often occur in axillary fascicles.

Varieties 3 (3 in the flora): sw United States, nw Mexico.

1 Leaves 50–150 mm; florets 20–27; phyllaryapices spinulose-aristate   1b Isocoma acradenia var. bracteosa
+ Leaves 20–50 mm; florets 12–24; phyllary apices usually rounded, not spinulose, sometimes with weakly developed aristae   (2)
2 (1) Leaves usually entire, proximal rarely toothed or lobed   1a Isocoma acradenia var. acradenia
+ Leaves all toothed to pinnatifid   1c Isocoma acradenia var. eremophila


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