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Key to families | Table of families and genera

Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.

 

GAMOCHAETA CUDWEED

Guy L. Nesom & Thomas J. Rosatti


Annual to short-lived perennial herb; taprooted or fibrous-rooted. Stem: erect to ± ascending. Leaf: basal and cauline, ± sessile, linear to oblanceolate or spoon-shaped, entire, base tapered to ± cordate, generally ± densely tomentose. Inflorescence: heads disciform, generally in tight groups in generally spike- or panicle-like clusters, reduced to terminal cluster in small plants; involucre cylindric to ± urn-shaped, ± bell-shaped when pressed; phyllaries graduated in 3–7 series, bases stiff-papery to scarious, margins and tips transparent-membranous, often shiny, generally ± brown to straw-colored; receptacle flat, concave in fruit, smooth, epaleate. Pistillate flower: pistillate 50–130; corolla narrowly tubular, yellow or distally ± purple to purple- to yellow-brown. Disk flower: 2–7; corolla yellow or distally ± purple or purple- to yellow-brown; anther tip triangular; style tips truncate, hair-tufted. Fruit: oblong, slightly flattened, faces papillate; pappus bristles in 1 series, basally fused, deciduous in ring.
± 50 species: native to America, some species widely naturalized. (Greek: united hair, for pappus bristles) [Nesom 2006 FNANM 19:431–438; Strother et al. 2012 Phytoneuron 2012–52:1–5]

Key to Gamochaeta

1. Leaf faces contrasting in color, adaxially ± glabrous to ± cobwebby-tomentose, abaxially white-felty tomentose

2. Adaxial leaf face ± glabrous; involucre ± purple, 2.5–3 mm, base glabrous; outer phyllaries elliptic-obovate to widely ovate-elliptic, rounded to obtuse; disk flowers 2–3; fruit 0.5–0.6 mm ..... G. coarctata

2' Adaxial leaf face ± sparsely cobwebby-tomentose; involucre ± brown, 3–5 mm, embedded in woolly hairs, base often sparsely cobwebby; outer phyllaries and flattened tips of inner dark or ± green-brown, ovate to ovate-lanceolate or widely ovate-triangular, truncate-rounded or acute to acuminate; disk flowers (3)4–6; fruit 0.5–0.8 mm

3. Involucre 3–3.5 mm; head clusters 10–12 mm wide (pressed); outer phyllaries ovate to ovate-lanceolate; fruit 0.5–0.6 mm ..... G. argyrinea

3' Involucre 4.5–5 mm; head clusters 12–18 mm wide (pressed); outer phyllaries widely ovate-triangular; fruit 0.7–0.8 mm ..... G. ustulata

1' Leaf faces not or weakly contrasting in color, ± green or gray-green, loosely tomentose or cobwebby, sometimes ± felty, sometimes adaxially ± glabrous in Gamochaeta stagnalis

4. Basal and proximal cauline leaves 4–16 mm wide; bracts among heads, cauline leaves oblanceolate to spoon-shaped, at least proximal bracts surpassing clusters of heads ..... G. pensylvanica

4' Basal and proximal cauline leaves 2–9 mm wide; bracts among heads, mid to distal cauline leaves generally linear to ± oblanceolate, bracts surpassing heads or not

5. Mid and distal cauline leaves oblanceolate, ± clasping; bracts among heads generally < clusters; involucre 3.5–4 mm; phyllaries in 4–5 series ..... [G. stachydifolia]

5' Mid and distal cauline leaves linear to lanceolate, oblanceolate, or spoon-shaped, not ± clasping; bracts among heads < or > than clusters; involucre 2.5–3.5 mm; phyllaries in 3–4(5) or 5–7 series

6. Involucre 3–3.5 mm, not purple, base generally ± glabrous to occasionally sparsely cobwebby; phyllaries in 5–7 series, outer ovate-triangular, 1/3–1/2 × inner, acute-acuminate; flower Jun–Jul ..... G. calviceps

6' Involucre 2.5–3 mm, generally ± purple proximally, base cobwebby; phyllaries in 3–4(5) series, outer ovate-triangular, 1/2–2/3 × inner, acute; flower Mar–Apr ..... G. stagnalis

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Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].
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