|Jepson Flora Project: Jepson Interchange|
|TREATMENT FROM THE JEPSON MANUAL (1993)||
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Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California
AND IS MAINTAINED FOR ARCHIVAL PURPOSES ONLY
Annual to tree
Leaves basal or cauline, alternate to whorled, simple to compound
Inflorescence: 1° inflorescence a head, each resembling a flower, 1many, generally arrayed in cymes, generally subtended by ± calyx-like involucre; flowers 1many 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)45; stamens 45, 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):128. See glossary p. 25 for illustrations of general family characteristics.
Annual, gray to green, cobwebby to tomentose
Stems generally several from base, generally spreading, < 20 cm, ± forked; central axis generally 0 or not dominant
Leaves simple, generally opposite, ± sessile, < 3 cm, ± obtuse, entire (uppermost ± alternate or seeming whorled, generally ± appressed to heads)
Inflorescence: heads disciform, sessile, solitary or in small groups, generally spheric; bracts like leaves; phyllaries 0; receptacle 12 X > wide, ± obovoid, generally entire, chaffy; chaff scales each enclosing a pistillate flower, falling with a fruit, length generally < 3 X width, generally ± obovoid, bulged upward, woolly, net-veined, tip scarious-winged, offset to inner edge, generally ± 2/3 the distance from base to top of scale, projected inward, beak-like, hidden in head
Pistillate flowers in many series, each subtended by a chaff scale; corollas tubular
Disk flowers staminate, 210, not subtended by chaff scales; ovary vestigial
Fruit smooth, shiny; pappus 0
Species in genus: 35 ill-defined species: w North America, s South America
Etymology: (Greek: slender chaff)
Reference: [Cronquist 1950 Res Stud State Coll WA 18:7189]
Spp. appear to intergrade, need detailed study.
Plants generally silky-tomentose
Stems generally several from base, spreading; central axis 0 or not dominant
Leaves: uppermost linear to narrowly oblanceolate, longest 1220 mm, generally 612 X > wide
Inflorescence: largest head 46 mm; longest chaff scale 1.52.7 mm
Disk flowers 0.71.4 mm, generally 4-lobed
Fruit 0.61.2 mm, ± cylindric
Ecology: Vernal pools, rarely moist slopes
Elevation: 101500 m.
Bioregional distribution: n California Floristic Province (rare and doubtful in s California Floristic Province), Modoc Plateau
Distribution outside California: to Washington, Idaho, Baja California?
[misspelled P. oreganus ] Highly variable; apparently intergrades with P. tenellus var. t., especially in s CA-FP, Baja CA.