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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.

 

PSOROTHAMNUS INDIGO-BUSH

Martin F. Wojciechowski & Duane Isely


Perennial herb to small tree, generally thorny, gland-dotted, especially stems, generally hairy. Stem: generally intricately branched. Leaf: simple or generally odd-1-pinnate, leaflets 1–3, generally more. Inflorescence: axillary or terminal, raceme, spike- or head-like or not; pedicel bractlets (0)2. Flower: calyx lobes generally unequal, upper 2 often largest; petals from receptacle, indigo blue to pink-purple; stamens 10, filaments partly fused; ovules generally 2. Fruit: indehiscent, included in or exserted from calyx, generally glandular. Seed: 1.
9 species: deserts of southwestern United States, Mexico, basins of Colorado Plateau. (Greek: scabshrub)
Unabridged references: [Barneby 1977 Mem New York Bot Gard 27:21–54, 598–607]

Key to Psorothamnus

1. Leaf simple, linear or oblanceolate (or leaflets 2–3)

2. Leaves persistent; inflorescence axis not ending as thorn ..... P. schottii

2' Leaves deciduous by early summer; inflorescence axis ending as thorn ..... P. spinosus

1' Leaves odd-1-pinnate or some simple

3. Fruit 2–4.5 mm, included; inflorescence dense; pedicel bractlets 0

4. Terminal leaflets > lateral or not; glands of twigs << 0.5 mm wide ..... P. emoryi

4' Terminal leaflets ± = lateral; glands of twigs ± 0.5 mm wide ..... P. polydenius

3' Fruit 7–10 mm, exserted; inflorescence ± open; pedicel bractlets 2

5. Fruit glands many, small, in longitudinal lines especially distally; leaves generally silvery-strigose; Mojave Desert, e Sonoran Desert, ..... P. fremontii

6. Leaflet linear, < ± 1 mm wide; e Sonoran Desert ..... var. attenuatus

6' Leaflet narrowly elliptic to ovate or obovate, ± 1.5–3 mm wide; Mojave Desert ..... var. fremontii

5' Fruit glands few to several, large, scattered; leaves variously hairy, generally not strigose; East of Sierra Nevada to San Bernardino Mountains, Desert ..... P. arborescens

7. Leaflets generally continuous with axis, silky-hairy ..... var. simplicifolius

7' Leaflets generally (or at least some) jointed to axis, glabrous to hairy, including silky-hairy or not

8. Calyx 7–9 mm, sparsely to densely hairy ..... var. arborescens

8' Calyx 5–7 mm, hairs 0 or sparse ..... var. minutifolius

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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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