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BETULACEAE BIRCH FAMILY

John O. Sawyer, Jr.

Shrub, tree; monoecious. Stem: trunk < 35 m; bark smooth to scaly, peeling in thin layers or not, lenticels present or not. Leaf: simple, alternate, petioled, deciduous; stipules deciduous; blade ovate to elliptic, generally serrate, generally ± doubly so. Inflorescence: catkin, generally appearing before leaves, often clustered; bracts each subtending 2–3 flowers, 3–6 bractlets. Staminate inflorescence: pendent, ± elongate. Pistillate inflorescence: pendent or erect, developing variously in fruit (see key to genera). Staminate flower: sepals 0–4, minute; petals 0; stamens 1–10; pistil vestigial or 0. Pistillate flower: sepals 0–4; petals 0; stamens 0; pistil 1, ovary inferior or superior, chambers 2, each 1-ovuled by abortion, stigmas 2. Fruit: achene, nut, winged or not, subtended or enclosed by 1–2 bracts.
6 genera, 155 species: generally northern hemisphere; some cultivated. [Furlow 1997 FNANM 3:507–538] —Scientific Editor: Thomas J. Rosatti.

Key to Betulaceae

CORYLUS HAZELNUT
Shrub, small tree. Stem: trunk < 6 m; bark smooth or scaly, dark brown; twigs glandular-hairy, becoming glabrous, brown; lenticels small; winter buds ciliate. Leaf: hairy; blade 4–10 cm, oblong to ovate, base oblique-cordate. Staminate inflorescence: 4–7 cm; bracts each subtending 3 flowers, 3 bractlets. Pistillate inflorescence: < 1 cm, appearing as terminal bud; bracts each subtending 2 flowers, 6 bractlets. Staminate flower: sepals 0; stamens 4. Pistillate flower: sepals 4; stigmas showy, red. Fruit: 1–2 per catkin, each enclosed in a papery involucre of 2 fused bracts, not winged.
15 species: northern hemisphere. (Latin: hazelnut, filbert) [Furlow 1997 Syst Bot 26:283–298] Flexible stems used in basket-making; some cultivated as food crop.

Previous taxon: Betula occidentalis
Next taxon: Corylus cornuta subsp. californica

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Oct 25 2014
Citation for this treatment: [Author of taxon treatment] 2013. Corylus, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=9116, accessed on Oct 25 2014

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