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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.

 

POPULUS COTTONWOOD
Tree. Stem: < 40 m; young bark smooth, pale yellow-green to gray; older bark furrowed, brown to gray; twigs with swellings below leaf scars; winter bud generally resinous, scales > 3. Leaf: juvenile, adult, late-season leaves may differ in size, shape, hairiness; generally glabrous; blade 3–11 cm, elliptic to deltate, veins pinnate or ± palmate, tip generally elongate. Inflorescence: catkin pendent, 3–8 cm; bract cut into narrow segments; flowers sessile; nectary a cup- or saucer-like disk. Flower: perianth modified into non-nectariferous, cup- or saucer-shaped structure. Staminate flower: stamens 8–60. Pistillate flower: style short, stigmas 2–3(4), large, scalloped to 2-lobed. Fruit: spheric to conic; valves 2–3(4), 3–12 mm.
40 species: northern hemisphere. (Latin: name for plants of this genus) [Hamzeh et al. 2006 J Torrey Bot Soc 133:519–527]
Unabridged references: [Hamzeh & Dayanandan 2004 Amer J Bot 91:1398–1408]

Key to Populus

1. Leaf blade white-tomentose abaxially ..... P. alba

1' Leaf blade glabrous or hairy abaxially

2. Leaf blade lanceolate ..... P. angustifolia

2' Leaf blade ovate, ± round, elliptic, rhomboid, or deltate (sometimes lanceolate on suckers or stressed plants of Populus trichocarpa)

3. Leaf blade rhomboid or deltate, margin crenate, serrate, or coarsely scalloped

4. Leaf blade deltate, margin coarsely scalloped ..... P. fremontii subsp. fremontii

4' Leaf blade deltate to rhomboid, margin crenate to serrate ..... P. nigra

3' Leaf blade ovate to ± round, margin finely scalloped

5. Leaf blade widely ovate to ± round, 2–4(7) cm, petiole laterally compressed ..... P. tremuloides

5' Leaf blade narrowly to widely ovate (sometimes lanceolate on suckers or stressed plants), 3–7 cm; petiole abaxially round, adaxially channeled ..... P. trichocarpa

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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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