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Trees or shrubs deciduous, monoecious. Stipules present, free, often deciduous, rarely persistent. Leaves alternate, simple, petiolate, usually doubly serrate, rarely simply serrate, lobulate, or entire; veins pinnate. Flowers unisexual. Male inflorescence precocious, elongate, pendulous, with numerous overlapping bracts; each bract usually subtending a small dichasium with 1-3 male flowers; stamens as many as and opposite sepals or, if sepals obsolete, then stamens of inflorescence to 20; filaments very short, connate or nearly so; anthers 2-loculed, thecae connate or separate, opening by longitudinal slits. Female inflorescence pendulous or erect, with numerous overlapping bracts; each bract subtending a small dichasium with 2 or 3 flowers; calyx with 1-6 scalelike lobes, or obsolete; petals absent; ovary inferior, 2-loculed; styles 2, free; ovules 2, or 1 by abortion, pendulous from near apex of each locule. Fruit a nut or nutlet, winged or not. Seed 1, with straight embryo and flat or thickened cotyledons, without endosperm.

Six genera and 150-200 species: mainly in Asia, Europe, and North and South America; six genera (one endemic) and 89 species (56 endemic) in China.

Because of evolutionary divergence within the Betulaceae, the family has often been divided into tribes (i.e., Betuleae, Carpineae, and Coryleae) or more recently into subfamilies (J. J. Furlow, J. Arnold Arbor. 71: 1-67. 1990) .^[1]

Photos

Map

Taxonomy

Genera

Alnaster

At least 5 species and subspecies belong to the Genus Alnaster.

More info about the Genus Alnaster may be found here.

Alnobetula

More info about the Genus Alnobetula may be found here.

Alnus

Trees or shrubs, to 35 m; trunks usually several, branching excurrent to deliquescent. Bark of trunks and branches light gray to dark brown, thin, smooth, close; lenticels often present, pale, prominent, sometimes horizontally expanded. Wood nearly white, turning reddish upon exposure to air, moderately light and soft, texture fine. Branches, branchlets, and twigs nearly 2-ranked to diffuse; young twigs uniform or ( Alnus subg. Alnobetula ) differentiated into long and short shoots. Winter buds stipitate (nearly sessile in Alnus subg. Alnobetula ), narrowly to broadly ovoid or ellipsoid, terete, apex acute to rounded; scales 2--3, valvate, or ( Alnus subg. Alnobetula ) several, imbricate, smooth, or ( Alnus subg. Clethropsis ) sometimes none. Leaves borne on long or short shoots, 3-ranked to nearly 2-ranked. Leaf blade ovate to elliptic or obovate, thin to leathery, base variable, cuneate to rounded, margins doubly serrate, serrate, serrulate, or nearly entire, apex variable, acute to obtuse or acuminate to rounded; surfaces glabrous to tomentose, abaxially sometimes resinous-glandular. Inflorescences: staminate catkins lateral, in racemose clusters or ( Alnus subg. Clethropsis ) solitary, formed ( Alnus subg. Alnus and Clethropsis ) during previous growing season and exposed or enclosed in buds during winter, or ( Alnus subg. Clethropsis ) formed and expanding during same growing season, expanding before or with leaves; pistillate catkins proximal to staminate catkins, solitary or in relatively small racemose clusters, erect to nearly pendulous, ovoid to ellipsoid, firm; scales and flowers crowded, developing and maturing at same time as staminate catkins. Staminate flowers in catkins, 3 per scale; stamens (3--) 4(--6) ; anthers and filaments undivided. Pistillate flowers usually 2 per scale. Infructescences erect or pendulous; scales persistent long after release of fruits, with 5 lobes, greatly thickened, woody. Fruits tiny samaras, lateral wings 2, leathery or membranaceous, reduced or essentially absent in some species. x = 7.^[2] [more]

At least 259 species and subspecies belong to the Genus Alnus.

More info about the Genus Alnus may be found here.

Asterocarpinus

More info about the Genus Asterocarpinus may be found here.

Betula

Trees or shrubs, to 30 m; trunks often several, branching excurrent, becoming deliquescent. Bark of trunks and branches dark brown to chalky white, smooth, often exfoliating; lenticels dark, prominent, sometimes horizontally expanded. Wood nearly white to reddish brown, light and soft to moderately heavy and hard, texture fine. Branches, branchlets, and twigs nearly 2-ranked; young twigs differentiated into long and short shoots, sometimes with taste and odor of wintergreen. Winter buds sessile, slender, terete, apex acute; scales several, imbricate, smooth. Leaves mostly on short shoots, nearly 2-ranked. Leaf blade ovate to deltate, elliptic, or nearly orbiculate, 0.5--10(--14) × 0.5--8 cm, thin, margins doubly serrate or serrate (or crenate to shallowly round-lobed in dwarf northern species) ; surfaces glabrous to tomentose, sometimes abaxially resinous-glandular. Inflorescences: staminate catkins mostly terminal on branchlets, solitary or in small racemose clusters, formed previous growing season and often exposed during winter, expanding with leaves; pistillate catkins proximal to staminate catkins, mostly solitary, erect, ovoid to cylindric, firm; scales and flowers crowded, enclosed within buds during winter, expanding with leaves. Staminate flowers in catkins 3 per scale; stamens (1--) 2--3(--4), filaments divided below anthers, nearly to base. Pistillate flowers (1--) 3 per scale. Infructescences erect or pendulous; scales usually deciduous with release of fruits (although persisting into winter in a few species), (1--) 3-lobed, thickened or leathery but not woody. Fruits samaras, lateral wings 2, moderately wide to broad, membranaceous. x = 14.^[3] [more]

At least 589 species and subspecies belong to the Genus Betula.

More info about the Genus Betula may be found here.

Betula-alnus

More info about the Genus Betula-alnus may be found here.

Betulites

At least 6 species and subspecies belong to the Genus Betulites.

More info about the Genus Betulites may be found here.

Carpinus

Trees, 8--25 m; trunks usually 1, branching mostly deliquescent, trunk and branches irregularly longitudinally ridged, fluted. Bark of trunk and branches bluish to brownish gray, thin, smooth, close [thicker, broken or shredded]; lenticels generally inconspicuous. Wood nearly white to light brown, very hard and heavy, texture fine. Branches, branchlets, and twigs conspicuously 2-ranked; young twigs differentiated into long and short shoots. Winter buds sessile, ovoid, 4-angled in cross section, apex acute; scales many, imbricate, smooth. Leaves on long and short shoots, 2-ranked. Leaf blade narrowly ovate to ovate, elliptic, or obovate with 10 or more pairs of lateral veins, 3--12 × 3--6 cm, thin, margins doubly serrate to serrulate; surfaces abaxially glabrous to tomentose, sometimes covered with small glands. Inflorescences: staminate catkins solitary or in small racemose clusters, lateral, formed previous growing season and enclosed [exposed] in buds during winter, expanding with leaves; pistillate catkins distal to staminate on short, leafy new growth, solitary, ± erect, elongate; bracts and flowers uncrowded. Staminate flowers in catkins 3 per scale, crowded together on pilose receptacle; stamens 3(--6), short; filaments often distinct part way to base; anthers divided into 2 parts, each 1-locular, apex pilose, Pistillate flowers 2 per bract. Infructescences loose racemose clusters of paired bracts, clusters pendulous, elongate; paired bracts deciduous with fruit, expanded, (1--) 3-lobed, variously toothed, foliaceous, each bract subtending 1 fruit. Fruits small nutlets, deltoid, longitudinally ribbed, often crowned with persistent sepals and styles. x = 8.^[4] [more]

At least 149 species and subspecies belong to the Genus Carpinus.

More info about the Genus Carpinus may be found here.

Catryla

More info about the Genus Catryla may be found here.

Corylus

Shrubs and trees, 3--15 m; tree trunks usually 1, branching mostly deliquescent, trunks and branches terete. Bark grayish brown, thin, smooth, close, breaking into vertical strips and scales in age; prominent lenticels absent. Wood nearly white to light brown, moderately hard, heavy, texture fine. Branches, branchlets, and twigs nearly 2-ranked to diffuse; young twigs differentiated into long and short shoots. Winter buds sessile, broadly ovoid, apex acute; scales several, imbricate, smooth. Leaves on long and short shoots, 2-ranked. Leaf blade broadly ovate with 8 or fewer pairs of lateral veins, 4--12 × 3.5--12 cm, thin, bases often cordate, margins doubly serrate, apex occasionally nearly lobed; surfaces abaxially usually pubescent, sometimes glandular. Inflorescences: staminate catkins on short shoots lateral on branchlets, in numerous racemose clusters, formed previous growing season and exposed during winter, expanding well before leaves; pistillate catkins distal to staminate catkins, in small clusters of flowers and bracts, reduced, only styles protruding from buds containing them at anthesis, expanding at same time as staminate. Staminate flowers in catkins 3 per scale, congested; stamens 4, divided nearly to base to form 8 half-stamens; filaments very short, adnate with 2 bractlets to bract. Pistillate flowers 2 per bract. Infructescences compact clusters of several fruits, each subtended and surrounded by involucre of bracts, bracts 2, hairy [spiny], expanded, foliaceous, sometimes connate into short to elongate tube. Fruits relatively thin-walled nuts, nearly globose to ovoid, somewhat laterally compressed, longitudinally ribbed. x = 11.^[5] [more]

At least 301 species and subspecies belong to the Genus Corylus.

More info about the Genus Corylus may be found here.

Duschekia

More info about the Genus Duschekia may be found here.

Osthrya

More info about the Genus Osthrya may be found here.

Ostrya

Trees, 9--18 m; trunks usually 1, branching mostly deliquescent, trunk and branches terete. Bark of trunk and branches brownish gray to light brown, thin, smooth, breaking and shredding into shaggy vertical strips and scales; lenticels generally inconspicuous. Wood nearly white to light brown, very hard and heavy, texture fine. Branches, branchlets, and twigs conspicuously 2-ranked; young twigs differentiated into long and short shoots. Winter buds sessile, ovoid, somewhat laterally compressed, apex acute; scales many, imbricate, longitudinally striate. Leaves on long and short shoots, 2-ranked. Leaf blade narrowly ovate to ovate, elliptic, or obovate with 10 or more pairs of lateral veins, 2.5--13 × 1.5--6 cm, thin, margins doubly serrate to serrulate; surfaces abaxially glabrous to tomentose. Inflorescences: staminate catkins terminal on branches, mostly in small, racemose clusters, formed previous growing season and exposed during winter, expanding with leaves; pistillate catkins proximal to staminate on short, lateral, leafy new growth, solitary, ± erect, elongate, bracts and flowers uncrowded. Staminate flowers in catkins 3 per bract, crowded together on pilose receptacle; stamens 3(--6), short; filaments often divided part way to base; anthers divided into 2 parts, each 1-locular, apex pilose. Pistillate flowers 2 per bract. Infructescences loosely imbricate, strobiloid clusters of closed inflated bracts; clusters pendulous, elongate; bracts deciduous with fruit, inflated, bladderlike, each bract enclosing 1 fruit. Fruits small nutlets, ovoid, longitudinally ribbed, often crowned with persistent sepals and styles. x = 8.^[6] [more]

At least 35 species and subspecies belong to the Genus Ostrya.

More info about the Genus Ostrya may be found here.

Ostryopsis

Shrubs deciduous. Leaves alternate, petiolate, usually irregularly and doubly serrate or incised. Male inflorescence enclosed by buds during winter, subsessile, terminal or lateral, spicate-cymose, cylindric; bracts numerous, overlapping; each bract subtending 1 male flower; bracteoles absent; stamens 4-8, inserted at base of bracts; anthers with 2 connate thecae, without hairs at apex. Female inflorescence terminal or axillary, racemose-capitulate; bracts forming a tubular sheath, leathery, lobed at apex; flowers paired, enclosed by bracts. Nutlet ovoid-globose, with prominent ribs, completely enclosed by bracts.^[7] [more]

More info about the Genus Ostryopsis may be found here.

Paracarpinus

More info about the Genus Paracarpinus may be found here.

Bibliography

• Alam, M. T. and W. F. Grant. 1972. Interspecific hybridization in birch (Betula). Naturaliste Canad. 99: 33--40.
• Brittain, W. H. and W. F. Grant. 1965. Observations on Canadian birch (Betula) collections at the Morgan Arboretum. I. B. papyrifera in eastern Canada. Canad. Field-Naturalist 79: 189--197.
• Drumke, J. S. 1965. A systematic survey of Corylus in North America. Diss. Abstr. 25: 4925--4926.
• Fernald, M. L. 1936b. Plants from the outer coastal plain of Virginia. Rhodora 38: 376--404, 414--452.
• Fernald, M. L. 1945. Some North American Corylaceae (Betulaceae). 1. Notes on Betula in eastern North America. Rhodora 47: 303--329.
• Fredskild, B. 1991. The genus Betula in Greenland---Holocene history, present distribution, and synecology. Nordic J. Bot. 11: 393--412.
• Furlow, J. J. 1979. The systematics of the American species of Alnus (Betulaceae). Rhodora 81: 1--121, 151--248.
• Furlow, J. J. 1987. The Carpinus caroliniana complex in North America. I. A multivariate analysis of geographical variation. Syst. Bot. 12: 21--40.
• Furlow, J. J. 1987b. The Carpinus caroliniana complex in North America. II. Systematics. Syst. Bot. 12: 416--434.
• Grant, W. F. and B. K. Thompson. 1975. Observations on Canadian birches, Betula cordifolia, B. populifolia, B. papyrifera and B. × caerulea. Canad. J. Bot. 53: 1478--1490.
• Hylander, N. 1957. On cut-leaved and small-leaved forms of Alnus glutinosa and A. incana. Svensk Bot. Tidskr. 51: 437--453.
• Johnsson, H. 1945. Interspecific hybridization within the genus Betula. Hereditas (Lund) 31: 163--176.
• Kasapligil, B. 1964. A contribution to the histotaxonomy of Corylus (Betulaceae). Adansonia, n. s. 4: 43--90.
• Lepage, E. 1976. Les bouleaux arbustifs du Canada et de Alaska. Naturaliste Canad. 103: 215--233.
• Li Pei-chun & Cheng Sze-hsu. 1979. Betulaceae. In: Kuang Ko-zen & Li Pei-chun, eds., Fl. Reipubl. Popularis Sin. 21: 44-137.
• Murai, S. 1964. Phytotaxonomical and geobotanical studies on gen. Alnus in Japan (III). Taxonomy of whole world species and distribution of each sect. Bull. Gov. Forest Exp. Sta. 171: 1--107.
• Rose, J. N. 1895. Notes upon Corylus rostrata and C. californica. Gard. & Forest 8: 263.
• Sulkinoja, M. 1990. Hybridization, introgression and taxonomy of the mountain birch in SW Greenland compared with related results from Iceland and Finnish Lapland. Meddel. Grfnland, Biosci. 33: 21--29.
• Trappe, J. M., J. F. Franklin, R. F. Tarrant, and G. M. Hansen, eds. 1968. Biology of Alder.... Portland.
• Wiegand, K. M. 1909. Recognition of Corylus rostrata and Corylus americana. Rhodora 11: 107.
• Winkler, H. 1914. Neue Revision der Gattung Carpinus. Bot. Jahrb. Syst. 15(suppl.): 488--508.
• Winstead, J. E., B. J. Smith, and G. I. Wardell. 1977. Fruit weight clines in populations of ash, ironwood, cherry, dogwood and maple. Castanea 42: 56--60.

Footnotes

1. Pei-chun Li & Alexei K. Skvortsov "Betulaceae". in Flora of China Vol. 4 Page 286. Published by Science Press (Beijing) and Missouri Botanical Garden Press. Online at EFloras.org.
2. "Alnus". in Flora of North America Vol. 3. Oxford University Press. Online at EFloras.org.
3. "Betula". in Flora of North America Vol. 3. Oxford University Press. Online at EFloras.org.
4. "Carpinus". in Flora of North America Vol. 3. Oxford University Press. Online at EFloras.org.
5. "Corylus". in Flora of North America Vol. 3. Oxford University Press. Online at EFloras.org.
6. "Ostrya". in Flora of North America Vol. 3. Oxford University Press. Online at EFloras.org.
7. "Ostryopsis". in Flora of China Vol. 4 Page 289. Published by Science Press (Beijing) and Missouri Botanical Garden Press. Online at EFloras.org.

Sources

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