View source for Betulaceae

{{Treatment/ID
|accepted_name=Betulaceae
|accepted_authority=Gray
|publications=
|common_names=Birch Family
|basionyms=
|synonyms=
|hierarchy=Betulaceae
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Betulaceae]]</div></div>
|volume=Volume 3
|mention_page=
|treatment_page=page 507
}}<!--

--><span class="statement" id="st-d0_s0" data-properties="whole_organism duration;whole_organism growth form;whole_organism duration;whole_organism growth form"><b>Trees </b>and shrubs, deciduous.</span> <span class="statement" id="st-d0_s1" data-properties="bud season;bud architecture;bud architecture;bud quantity;scale arrangement or dehiscence;scale quantity;scale arrangement"><b>Winter </b>buds stipitate or sessile, with either 2–3 valvate scales (stipules) or few-to-many imbricate scales (or occasionally naked);</span> <span class="statement" id="st-d0_s2" data-properties="terminal bud presence">terminal bud absent.</span> <span class="statement" id="st-d0_s3" data-properties="leaf arrangement;leaf arrangement;leaf arrangement;leaf architecture"><b>Leaves </b>alternate, spirally arranged, 2–3-ranked, simple;</span> <span class="statement" id="st-d0_s4" data-properties="stipule duration;stipule fusion">stipules deciduous, distinct;</span> <span class="statement" id="st-d0_s5" data-properties="petiole presence">petioles present.</span> <span class="statement" id="st-d0_s6" data-properties="leaf-blade shape;leaf-blade architecture;margin shape;margin architecture or shape"><b>Leaf-</b>blade sometimes lobed, pinnately veined, margins toothed, serrate to nearly entire;</span> <span class="statement" id="st-d0_s7" data-properties="surface pubescence;gland coating">surfaces glabrous to tomentose, abaxially often with resinous glands.</span> <span class="statement" id="st-d0_s8" data-properties="inflorescence reproduction"><b>Inflorescences </b>unisexual;</span> <span class="statement" id="st-d0_s9" data-properties="catkin architecture;catkin orientation;catkin shape;catkin shape;catkin architecture">staminate catkins pendulous, elongate, cylindric, conspicuously bracteate, consisting of crowded, reduced, 1–3-flowered clusters;</span> <span class="statement" id="st-d0_s10" data-properties="catkin inflorescence architecture;catkin orientation;catkin architecture;subtended architecture or arrangement;subtended architecture;subtended arrangement;involucre architecture">pistillate inflorescences either of erect to pendulous bracteate catkins, or of compact 2–3-flowered clusters subtended by leafy involucres;</span> <span class="statement" id="st-d0_s11" data-properties="bract architecture;bract texture">bracts often nearly foliaceous or woody in infructescences.</span> <span class="statement" id="st-d0_s12" data-properties="flower architecture;flower architecture"><b>Staminate </b>flowers bracteate;</span> <span class="statement" id="st-d0_s13" data-properties="stamen atypical quantity;stamen quantity">stamens (1–) 4–6;</span> <span class="statement" id="st-d0_s14" data-properties="anther architecture or structure in adjective form;anther dehiscence;slit dehiscence or orientation;pollen-sac fusion">anthers 2-locular, dehiscing by longitudinal slits, pollen-sacs often ± distinct;</span> <span class="statement" id="st-d0_s15" data-properties="pistillode presence">pistillode sometimes present.</span> <span class="statement" id="st-d0_s16" data-properties="flower architecture;flower size;flower size"><b>Pistillate </b>flowers small, highly reduced;</span> <span class="statement" id="st-d0_s17" data-properties="pistil quantity;pistil architecture">pistil 1, 2 (–3) -carpellate;</span> <span class="statement" id="st-d0_s18" data-properties="">ovary inferior, usually 2-locular proximally, 1-locular distally;</span> <span class="statement" id="st-d0_s19" data-properties="ovary position;ovary architecture or structure in adjective form;ovary architecture or structure in adjective form;ovary placentation">placentation axile;</span> <span class="statement" id="st-d0_s20" data-properties="ovule quantity;ovule orientation">ovules 1–2 per locule, pendulous;</span> <span class="statement" id="st-d0_s21" data-properties="style quantity;style fusion;style fusion">styles 2, distinct or nearly so;</span> <span class="statement" id="st-d0_s22" data-properties="stigma condition or texture">stigmas dry;</span> <span class="statement" id="st-d0_s23" data-properties="staminode presence">staminodes usually absent.</span> <span class="statement" id="st-d0_s24" data-properties="nutlet architecture;samara architecture;samara architecture;cupule architecture;hull architecture;bract quantity"><b>Fruits </b>nuts, nutlets, or 2-winged samaras, 1-seeded, without multibracteate cupule, often subtended or enclosed by foliaceous hull developed from 2–3 bracts;</span> <span class="statement" id="st-d0_s25" data-properties="seed-coat texture">seed-coat membranous;</span> <span class="statement" id="st-d0_s26" data-properties="endosperm presence;endosperm width">endosperm present, thin at maturity;</span> <span class="statement" id="st-d0_s27" data-properties="embryo course">embryo straight, as long as seed;</span> <span class="statement" id="st-d0_s28" data-properties="cotyledon prominence or shape;cotyledon size or width;cotyledon coating">cotyledons flat or greatly thickened, oily.</span><!--

-->{{Treatment/Body
|distribution=Primarily boreal and cool temperate zones of Northern Hemisphere
|discussion=<p>Genera 6, species ca. 125 (5 genera, 33 species in the flora).</p><!--
--><p>Betulaceae belong to an ancient lineage, traceable in the fossil record to the upper Cretaceous. They are easily distinguished by their woody habit; simple, pinnately veined, usually ovate, sharp-toothed leaves; long staminate catkins that often develop the season before anthesis; and (except in Corylus and Ostryopsis) strobiluslike infructescences. The family is held together on the basis of many features, including habit, leaf structure and arrangement, trichome morphology, wood anatomy, inflorescence morphology, ovary and ovule structure, pollen morphology, embryo structure, and fertilization and germination patterns. Five of the six constituent genera inhabit the boreal and cool temperate zones of Eurasia, North America, and the mountains of Mexico and Central America, and two genera also grow in the Andes to northern Argentina in South America. The remaining genus, Ostryopsis Decaisne (most closely related to Corylus Linnaeus), consists of two species of shrubs restricted to northern and western China.</p><!--
--><p>The group is sometimes divided into two families, Betulaceae (Alnus and Betula) and Corylaceae (Carpinus, Ostrya, Corylus, and Ostryopsis), especially in Europe (e.g., H. K. Airy Shaw in J. C. Willis 1973; R. M. T. Dahlgren 1980; J. Hutchinson 1959). In America, this treatment has been followed by A. J. Rehder (1940), J. K. Small (1903), and a few others. Some of those writers have based their recognition of two families in part on the belief that a fundamental difference exists in the staminate inflorescences of the two groups. This view is no longer widely accepted, and most modern authors maintain the family as a single group composed of two subfamilies, Betuloideae and Coryloideae.</p><!--
--><p>Betulaceae may have been derived from hamamelidaceous stock (O. Tippo 1938); this idea has been advanced by others (e.g., J. A. Doyle 1969; P. K. Endress 1977; M. W. Chase et al. 1993). The ancestor of more advanced Hamamelidae (including Betulaceae) may have been a member of the Normapolles complex, a Cretaceous fossil pollen flora that includes grains similar in structure to those of the modern Betulaceae (J. A. Doyle 1969). The pollen of modern Betulaceae is much more specialized than that of modern Hamamelidales, however, and the relationships of the Normapolles complex to Juglandaceae, Fagaceae, and other amentiferous groups, as well as to Betulaceae, are not certain. Additional fossil information will be needed if botanists are to gain stronger insights into the phylogeny of these families (P. R. Crane 1989; K. C. Nixon 1989).</p><!--
--><p>The most obvious evolutionary trends within the family are those related to fruit dispersal (winged fruits in the Betuloideae, nutlets with accessory winglike bracts in Carpinus and Ostrya, and dispersal by small mammals in Corylus), and with apparent adaptations for survival in cold climates (including shrubby growth forms, small leaves, and the protection of pistillate catkins during winter by bud scales in boreal species). Some radiation has also occurred with respect to the pollination system (E. J. Jäger 1980). Please see P. R. Crane (1989) and J. J. Furlow (1990) for reviews of literature related to the origin and diversification of the family.</p><!--
--><p>Members of Betulaceae are economically important as timber trees, as the source of hazelnuts and filberts (Corylus), as ornamental trees and shrubs, and as aids in soil nitrification and stabilization (Alnus). Some are important as causes of pollen allergies in regions where they grow abundantly.</p>
|tables=
|references=
}}<!--

--><div class="treatment-key">
==Key==
<div class="treatment-key-group">
  
{| class="wikitable fna-keytable"
|-id=key-0-1
|1
|Infructescences 1-4 cm, conelike, of small, crowded, woody or leathery scales, these deciduous with fruits or persistent; fruits tiny samaras, laterally winged, wings sometimes reduced to ridges; pericarp thin, leathery (subfamily Betuloideae).
|[[#key-0-2| > 2]]
|-id=key-0-1
|1
|Infructescences mostly longer than 4 cm, of relatively uncrowded clusters with large, nearly foliaceous bracts, these deciduous with fruits; fruits tiny to moderately large nuts, hard-shelled, not winged (subfamily Coryloideae).
|[[#key-0-3| > 3]]
|-id=key-0-2
|2
|Winter buds stipitate (nearly sessile in some species); stamens (3-)4(-6), anthers and filaments undivided; pistillate flowers 2 per scale; infructescence scales with 5 lobes, greatly thickened, woody, persistent long after release of fruits.
|[[Alnus|Alnus]]
|-id=key-0-2
|2
|Winter buds sessile; stamens usually (1-)2-3(-4), filaments divided below anthers; pistillate flowers (1-)3 per scale; infructescence scales with (1-)3 lobes, thickened or leathery but not woody, usually deciduous with release of fruits.
|[[Betula|Betula]]
|-id=key-0-3
|3
|Leaf blade broadly ovate to nearly orbiculate, lateral veins 8 or fewer pairs; infructescence irregular cluster of several nuts, each nut usually 1 cm or more, surrounded by involucre of several coarsely toothed, leaflike bracts, involucre sometimes long and tubular (tribe Coryleae).
|[[Corylus|Corylus]]
|-id=key-0-3
|3
|Leaf blade narrowly ovate to elliptic, lateral veins 10 or more pairs; infructescence elongate, loosely arranged racemose cluster of 3 or more pairs of leafy bracts, each bract either subtending or enclosing single nutlet, nutlet less than 0.8 cm (tribe Carpineae).
|[[#key-0-4| > 4]]
|-id=key-0-4
|4
|Infructescence bracts flat, open, (1-)3-lobed, variously toothed.
|[[Carpinus|Carpinus]]
|-id=key-0-4
|4
|Infructescence bracts forming inflated bladders, these completely enclosing fruits.
|[[Ostrya|Ostrya]]
|}
</div></div><!--

-->{{#Taxon:
name=Betulaceae
|author=John J. Furlow
|authority=Gray
|rank=family
|parent rank=
|synonyms=
|basionyms=
|family=Betulaceae
|illustrator=John Myers
|illustration copyright=Flora of North America Association
|distribution=Primarily boreal and cool temperate zones of Northern Hemisphere
|reference=None
|publication title=
|publication year=
|special status=
|source xml=https://bibilujan@bitbucket.org/aafc-mbb/fna-fine-grained-xml.git/src/84153f6d59a0a91d69695978a64cee7560374f8e/V3/V3_971.xml
|anther architecture or structure in adjective form=2-locular
|anther dehiscence=dehiscing
|bract architecture=foliaceous
|bract quantity=2;3
|bract texture=woody
|bud architecture=sessile;stipitate
|bud quantity=2;3
|bud season=winter
|catkin architecture=bracteate;bracteate;staminate
|catkin inflorescence architecture=pistillate
|catkin orientation=erect;pendulous
|catkin shape=cylindric;elongate
|cotyledon coating=oily
|cotyledon prominence or shape=flat
|cotyledon size or width=thickened
|cupule architecture=multibracteate
|embryo course=straight
|endosperm presence=absent
|endosperm width=thin
|flower architecture=pistillate;bracteate;staminate
|flower size=reduced;small
|gland coating=resinous
|hull architecture=foliaceous
|inflorescence reproduction=unisexual
|involucre architecture=leafy
|leaf architecture=simple
|leaf arrangement=2-3-ranked;arranged;alternate
|leaf-blade architecture=veined
|leaf-blade shape=lobed
|margin architecture or shape=serrate;nearly entire
|margin shape=toothed
|nutlet architecture=1-seeded
|ovary architecture or structure in adjective form=1-locular;2-locular
|ovary placentation=axile
|ovary position=inferior
|ovule orientation=pendulous
|ovule quantity=1;2
|petiole presence=absent
|pistil architecture=2(-3)-carpellate
|pistil quantity=1
|pistillode presence=absent
|pollen-sac fusion=distinct
|samara architecture=1-seeded;2-winged
|scale arrangement=imbricate
|scale arrangement or dehiscence=valvate
|scale quantity=few-to-many
|seed-coat texture=membranous
|slit dehiscence or orientation=longitudinal
|stamen atypical quantity=1;4
|stamen quantity=4;6
|staminode presence=absent
|stigma condition or texture=dry
|stipule duration=deciduous
|stipule fusion=distinct
|style fusion=nearly;distinct
|style quantity=2
|subtended architecture=2-3-flowered
|subtended architecture or arrangement=compact
|subtended arrangement=cluster
|surface pubescence=glabrous;tomentose
|terminal bud presence=absent
|whole_organism duration=deciduous;deciduous
|whole_organism growth form=shrub;tree
}}<!--

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