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FNA | Family List | FNA Vol. 20 | Asteraceae

171. Lorandersonia Urbatsch, R. P. Roberts & Neubig, Sida. 21: 1619. 2005.

Rabbitbush [For Loran Crittenden Anderson, b. 1936, fervent American enthusiast of Asteraceae, especially Chrysothamnus and related taxa]

Lowell E. Urbatsch, Roland P. Roberts, Kurt M. Neubig

Subshrubs or shrubs, 5–350 cm. Stems erect to ascending, often fastigiately or intricately branched (bark typically tan, becoming white to tan or gray when older; twigs usually greenish), glabrous or scabrous, gland-dotted (sometimes in pits), often resinous. Leaves cauline (usually persistent; often crowded, appressed or ascending to spreading, becoming deflexed); alternate; sessile or petiolate; blades prominently 1-nerved plus sometimes 1–2 pairs of collateral nerves, linear to oblong or lanceolate to narrowly oblanceolate or broadly spatulate (flat to concave), margins entire or coarsely serrate, sometimes ciliate, faces glabrous or scabrous, gland-dotted (sometimes in ± deep, resin-filled pits, sometimes sessile) or pustulate, often ± resinous. Heads discoid (radiate in L. microcephala and L. peirsonii; rays occasionally observed in L. spathulata), usually in congested, rounded, compound, usually cymiform to corymbiform, sometimes racemiform arrays. Involucres cylindric to obconic or hemispheric, (4–15 ×) 1.5–6 mm. Phyllaries 13–30 in 3–6 series (often in vertical ranks), green to tan, 1-nerved (midnerves obscure or evident, sometimes enlarged subapically and glandular; usually flat or convex, sometimes keeled), ovate to oblong or lanceolate to oblanceolate, strongly unequal or subequal, mostly chartaceous, outer sometimes herbaceous or herbaceous-tipped, margins scarious (apices erect or slightly spreading, acute, acuminate, cuspidate, or obtuse), faces often resinous, sometimes stipitate-glandular (in L. peirsonii). Receptacles convex, pitted, epaleate (sometimes bearing scales or awn-like projections). Ray florets 0 or (1–)6–20, pistillate, fertile; corollas pale to dark yellow. Disc florets 4–63, bisexual, fertile; corollas pale to dark yellow, tubes usually shorter than (about equaling in L. salicina) gradually dilated throats, lobes 5, spreading to recurved, lanceolate to triangular; style-branch appendages lanceolate or attenuate to subulate. Cypselae (mostly tan to brownish) oblong to obconic, subterete to prismatic, 4–12-ribbed, faces glabrous or densely hairy; pappi persistent, of 20–80+ tan subequal, fine, barbellate, apically ± clavate bristles in 1 series. x = 9.

Species 7 (7 in the flora): North America, n Mexico.

Phylogenetic studies (R. P. Roberts and L. E. Urbatsch 2004) support the monophyly of this taxon consisting of species formerly in Chrysothamnus, Hesperodoria, and Tonestus.

1 Heads radiate; subshrubs (mat-forming), 5–20 cm; phyllaries subequal; 2400+ m   (2)
+ Heads discoid; shrubs 25–350 cm; phyllaries unequal; usually below 2400 m   (3)
2 (1) Leaf blades elliptic to narrowly oblanceolate, margins scarious, entire; phyllary faces glabrous; ray florets 5–8, disc florets 10–15   3 Lorandersonia microcephala
+ Leaf blades broadly spatulate, margins coarsely serrate; phyllary faces stipitate-glandular; ray florets 16–20; disc florets 44–63   4 Lorandersonia peirsonii
3 (1) Involucres 10–15 mm; phyllaries in vertical ranks   (4)
+ Involucres 4–7.2 mm; phyllaries in spirals or in weak vertical ranks (in 5 vertical ranks in L. linifolia)   (5)
4 (3) Leaf margins ciliolate; New Mexico, adjacent states   1 Lorandersonia baileyi
+ Leaf margins eciliate; c New Mexico, adjacent Texas   5 Lorandersonia pulchella
5 (3) Twigs (and leaves) gland-dotted (in deep, circular, resin-filled pits); phyllaries (in spirals) unequal; involucres 4–5 mm; receptacles with 3–5 scales; nw Arizona   6 Lorandersonia salicina
+ Twigs glabrous or finely scabrous; leaf faces glabrous, scabridulous, or gland-dotted (in shallow, resin-filled pits); phyllaries (in 5 vertical ranks or in weak vertical ranks); involucres 4.5–7.2 mm; receptacles with 0–2 scales or awns; n, c Arizona eastward   (6)
6 (5) Cypselae densely hairy; branches glabrous or scabridulous; leaves linear to lanceolate or oblong (widest proximally), glabrous; phyllaries in 5 vertical ranks; plants soboliferous; ne New Mexico northward   2 Lorandersonia linifolia
+ Cypselae sparsely hairy; branches finely scabrous; leaves oblanceolate to spatulate (widest distally), scabridulous; phyllaries in weak vertical ranks; plants not soboliferous; s New Mexico, adjacent Texas   7 Lorandersonia spathulata

Lower Taxa


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