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Jepson Interchange (more information)
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David J. Keil, Family Editor and author, except as specified

Annual to tree
Leaves basal or cauline, alternate to whorled, simple to compound
Inflorescence: 1° inflorescence a head, each resembling a flower, 1–many, generally arrayed in cymes, generally subtended by ± calyx-like involucre; flowers 1–many per head
Flowers bisexual, unisexual, or sterile, ± small, of several types; calyx 0 or modified into pappus of bristles, scales, or awns, which is generally persistent in fruit; corolla radial or bilateral (rarely 0), lobes generally (0)4–5; stamens 4–5, anthers generally fused into cylinder around style, often appendaged at tips, bases, or both, filaments generally free, generally attached to corolla near throat; pistil 1, ovary inferior, 1-chambered, 1-seeded, style 1, branches 2, generally hair-tufted at tip, stigmas 2, generally on inside of style branches
Fruit: achene, cylindric to ovoid, generally deciduous with pappus attached
Genera in family: ± 1300 genera, 21,000 species (largest family of dicots): worldwide. Largest family in CA. Also see tribal key to CA genera: Strother 1997 Madroño 44(1):1–28. See glossary p. 25 for illustrations of general family characteristics.


Robert L. Carr and Gerald D. Carr

Species in genus: 1 sp
Etymology: (Greek: odor gland)


O. tenella Nutt.


Annual < 4 dm, ± densely glandular, ± scabrous and long-hairy, strongly scented; tack- or saucer-shaped glands 0
Stem erect; branchlets many, thread-like, ± spreading
Leaves alternate, sessile, reduced upward; lower 2–5 cm, linear, entire
Inflorescence: heads many, radiate, in cymes; peduncles spreading, bracts few, 5–8 mm, narrowly lanceolate; phyllaries 4–7 mm, partly enfolding ray fruit; chaff scales between ray and disk flowers, 4–7 mm, fused
Ray flowers 3–5; ligules deeply 3-lobed, white to reddish, sometimes red-spotted near base
Disk flowers 3–10; corolla colored like ligule; anthers yellow
Fruit: ray fruit 1.8–2.7 mm, back rounded to angled, rough, glabrous, inner surface ± flat, beak short, off-center, pappus 0; disk fruit ± angled, tapered at base, ± thinly hairy, pappus of ± 8 scales, long and short
Chromosomes: 2n=18
Ecology: UNCOMMON. Barren, often rocky, exposed hillsides, canyons
Elevation: < 600 m.
Bioregional distribution: Southwestern California (except Channel Islands)
Distribution outside California: Baja California
Synonyms: Calycadenia t. (Nutt.) Torr. & A. Gray

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