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Asteraceae
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Sue Carnahan
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Theodore M. Barkley+, Luc Brouillet, John L. Strother in Flora of North America (vol. 19, 20 and 21)
Annuals, biennials, perennials, subshrubs, shrubs, vines, or trees. Roots usually taproots, sometimes fibrous. Stems usually erect, sometimes prostrate to ascending (underground stems sometimes woody caudices or rhizomes, sometimes fleshy). Leaves usually alternate or opposite, sometimes in basal rosettes, rarely in whorls; rarely stipulate, usually petiolate, sometimes sessile, sometimes with bases decurrent onto stems; blades usually simple (margins sometimes 1-2+ times pinnatifid or palmatifid), rarely compound. Inflorescences indeterminate heads (also called capitula); each head usually comprising a surrounding involucre of phyllaries (involucral bracts), a receptacle, and (1-)5-300+ florets; individual heads sessile or each borne on a peduncle; heads borne singly or in usually determinate, rarely indeterminate, arrays (cymiform, corymbiform, racemiform, spiciform, etc.); involucres sometimes subtended by calyculi (sing. calyculus); phyllaries borne in 1-5(-15+) series proximal to (i.e., outside of or abaxial to) the florets; receptacles usually flat to convex, sometimes conic or columnar, either paleate (bearing paleae or receptacular bracts that individually subtend some or all of the florets) or epaleate (lacking paleae); epaleate receptacles sometimes bristly or hairy or bearing subulate enations among the florets. Florets bisexual, pistillate, functionally staminate, or neuter (also called neutral); sepals highly modifed (instead of ordinary sepals, each ovary usually bears a pappus of bristles, awns, and/or scales, sometimes in combination within a single pappus); petals connate, corollas (3-)5-merous, ± actinomorphic or zygomorphic (one or both kinds in a single head, see descriptions of radiate, discoid, liguliflorous, disciform, and radiant following); stamens (4-)5, alternate with corolla lobes, filaments inserted on corollas, usually distinct, anthers introrse, usually connate and forming tubes around styles (rarely filaments connate and anthers distinct; e.g., Heliantheae, Ambrosiinae); ovaries inferior, 2-carpellate, and 1-locular with 1 basally attached, anatropous ovule; styles 1 in each bisexual, functionally staminate, or pistillate floret; each style usually ringed at base by a nectary, distally 2-branched with stigmatic papillae borne on adaxial face of each branch in 2 separate or contiguous lines or in 1 continuous band (
Desert Research Learning Center, Botany Program

The largest angiosperm family with over 22,000 described species globally, it is also one of the most distinctive in terms of its floral morphology. In North America there are 418 genera and about 2,400 species. Variable growth form, resin canals and/or lactifers often present. Leaves simple or compound, spiral or opposite, exstipulate. Inflorescence one or more heads arranged into various types of secondary inflorescences, each head subtended by phyllaries (bracts), heads of five general types: discoid, disciform, radiate, ligulate, and bilabiate. Flowers perfect, imperfect or sterile, radial or bilateral, of three types: bilabiate, disk, or ray/ligulate. Sepals highly modified, forming pappus composed of 2-many scales or bristles that are variously shaped, often hairy, barbed or plumose. Corolla of 5 connate petals, variously shaped. Stamens 5, usually with connate anthers, plunger pollen presentation, 2 connate carpels, and inferior ovaries with basal placentation. Fruit an achene (cypselae), usually arranged in a multiple fruit.

Species within inventory project: Chicago Region Checklists and Inventories || << 1 - 50 taxa >>
Achillea millefolium
Image of Achillea millefolium
Achillea ptarmica
Image of Achillea ptarmica
Acroptilon repens
Image of Acroptilon repens
Ageratina altissima
Image of Ageratina altissima
Ambrosia artemisiifolia
Image of Ambrosia artemisiifolia
Ambrosia bidentata
Image of Ambrosia bidentata
Ambrosia psilostachya
Image of Ambrosia psilostachya
Ambrosia trifida
Image of Ambrosia trifida
Ambrosia × intergradiens
Image of Ambrosia × intergradiens
Anaphalis margaritacea
Image of Anaphalis margaritacea
Antennaria neglecta
Image of Antennaria neglecta
Antennaria parlinii
Image of Antennaria parlinii
Antennaria plantaginifolia
Image of Antennaria plantaginifolia
Anthemis arvensis
Image of Anthemis arvensis
Anthemis cotula
Image of Anthemis cotula
Arctium lappa
Image of Arctium lappa
Arctium minus
Image of Arctium minus
Arctium tomentosum
Image of Arctium tomentosum
Arnoglossum atriplicifolium
Image of Arnoglossum atriplicifolium
Arnoglossum plantagineum
Image of Arnoglossum plantagineum
Artemisia absinthium
Image of Artemisia absinthium
Artemisia annua
Image of Artemisia annua
Artemisia biennis
Image of Artemisia biennis
Artemisia campestris
Image of Artemisia campestris
Artemisia dracunculus
Image of Artemisia dracunculus
Artemisia frigida
Image of Artemisia frigida
Artemisia ludoviciana
Image of Artemisia ludoviciana
Artemisia serrata
Image of Artemisia serrata
Artemisia vulgaris
Image of Artemisia vulgaris
Aster chasei
Image of Aster chasei
Aster ciliolatus
Image of Aster ciliolatus
Aster parviceps
Image of Aster parviceps
Aster ptarmicoides
Image of Aster ptarmicoides
Aster racemosus
Image of Aster racemosus
Aster subasper
Image of Aster subasper
Aster turbinellus
Image of Aster turbinellus
Aster x amethystinus
Image of Aster x amethystinus
Bellis perennis
Image of Bellis perennis
Bidens aristosa
Image of Bidens aristosa
Bidens beckii
Image of Bidens beckii
Bidens bipinnata
Image of Bidens bipinnata
Bidens cernua
Image of Bidens cernua
Bidens connata
Image of Bidens connata
Bidens discoidea
Image of Bidens discoidea
Bidens frondosa
Image of Bidens frondosa
Bidens polylepis
Image of Bidens polylepis
Bidens trichosperma
Image of Bidens trichosperma
Bidens tripartita
Image of Bidens tripartita
Bidens vulgata
Image of Bidens vulgata
Boltonia asteroides
Image of Boltonia asteroides
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