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Key to families | Table of families and genera
This text currently parallels The Jepson Manual: Vascular Plants of California, Second Edition that is now available at the University of California Press.
Text appearing in blue on this page will not appear in the printed book; it will be displayed only on the Web. 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.
Annual, perennial herb [to shrub], weak, stinging hairs 0 or few to many; monoecious or dioecious.
Stem: branched or not, erect, spreading, or decumbent.
Leaf: opposite, lanceolate to cordate, toothed, prominently 3–5-veined from base; crystals round to elongate.
Inflorescence: head-, raceme-, or panicle-like.
Staminate flower: sepals 4, ± free, green, sharp-bristly; stamens 4.
Pistillate flower: sepals 4, ± free, outer 2 < inner 2.
Fruit: lenticular to deltate, enclosed by 2 inner sepals.
± 45 species: especially temperate. (Latin: to burn, from stinging hairs)
Unabridged references: [Woodland 1982 Syst Bot 7:282–290]
1. Annual 1–6(8) dm; leaf blade 18–40(90) mm; inflorescence generally ± head- or spike-like, often < petiole, of staminate and pistillate flowers; fruit deltate ..... U. urens
1' Perennial 5–30 dm; leaf blade 60–200 mm; inflorescence raceme- or panicle-like, generally > petiole, of staminate or pistillate flowers; fruit ovate ..... U. dioica
2. Non-stinging hairs on stem, leaf 0 to ± dense, occasionally > 1 mm, those on abaxial veins appressed; stem green ..... subsp. gracilis
2' Non-stinging hairs on stem, leaf dense, < 1 mm, those on abaxial veins erect; stem gray-green ..... subsp. holosericea
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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