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Asteraceae Group 3
See list of 24 genera in this group-
1a. Leaf blades spiny margined; involucral bracts tipped by a spine (the spine pinnately branched in Centaurea [Fig. 387])
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2a. Capitula 1-flowered, aggregated in clusters forming a false, ± spherical, secondary capitulum that is subtended by a common involucre [Fig. 398]; true involucre subtended by a tuft of capillary bristles
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2b. Capitula with more than 1 flower, not conspicuously aggregated in secondary capitula; involucre not subtended by a tuft of bristles
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3a. Pappus composed of 10 outer, longer, minutely barbellate awns and 10 inner, shorter, ciliate awns; cypsela body ± tetete in cross-section; inner involucral bracts tipped by a pectinately fringed and spine-tipped appendage or the apical spine pinnately or palmately branched [Fig. 387] (in part)
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3b. Pappus absent or composed of many rows of linear scales; cypsela body quadrangular in cross-section; inner involucral bracts lacking fringed appendages and tipped by a simple spine
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1b. Leaf blades without spiny margins, though spines may occur on other portions of the plant; involucral bracts not tipped by spines (except Ageratum; though they
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4a. Receptacle bristly setose, hairy, or chaffy, at least near the margin of the capitulum; corollas anthocyanic, cyanic, yellow to orange, green-yellow, green-white, or white (or lacking on some flowers)
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5a. Pappus of some form present, at least on the inner flowers
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6a. Most or all of the leaves opposite [Fig. 380]; pappus of 2–6 awns, these usually retrorsely barbellate (rarely antrorsely barbellate or smooth or absent) [Figs. 381, 382, 383]; receptacle with flattened scales (in part)
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6b. Leaves alternate; pappus of bristles or scales; receptacle densely bristly
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7a. Involucral bracts with an entire, attenuate, hooked tip [Fig. 377]; leaf blades 15–70 cm wide, usually simple, rounded to cordate at the base
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5b. Pappus absent
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8a. Receptacle densely bristly setose or long-hairy or naked
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9a. Most or all the involucral bracts tipped by an erose or a fimbriate- to pectinate-fringed appendage [Figs. 386,388,389]; involucre 10–25 mm tall; cypselas attached laterally to the receptacle; style branches with a thickened, often pubescent, ring, the texture of the branches changing to papillate distal to the ring (in part)
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9b. Involucral bracts with entire margins; involucre 1–7.5 mm tall; cypselas attached basally to the receptacle; style branches truncate and penicillate (in part)
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8b. Receptacle with scale-like chaff
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10a. Staminate and carpellate flowers in separate capitula, the staminate capitula usually the uppermost and possessing an undivided style; involucre armed with tubercles, spines, or prickles [Fig. 478]; carpellate flowers lacking a corolla
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11a. Staminate involucre of distinct bracts; carpellate involucre a conspicuous, prickly bur, 8–40 mm tall
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11b. Staminate involucre of connate bracts; carpellate involucre with 1 or more series of tubercles or spines [Fig. 371], 3–10 mm tall (in part)
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10b. Flowers bisexual or unisexual and then the staminate and carpellate flowers in the same capitulum; involucre unarmed; all the flowers with a corolla (except in Cyclachaena xanthiifolia, in which the carpellate flowers sometimes lack a corolla)
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12a. Plants woody; leaf blades white-tomentose, evergreen, 3-dimensionally pinnately dissected
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12b. Plants herbaceous or usually woody in Iva frutescens; leaf blades glabrous or pubescent, but not white-tomentose, deciduous, simple to 3-times pinnately divided, relatively plane
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13a. Involucre with 2 series of dimorphic bracts—the outer series larger, herbaceous to foliaceous, the inner series smaller, membranaceous, and usually striate [Fig. 381]; pappus of 2–6 awns, these usually retrosely barbellate (rarely antrorsely barbellate or smooth or absent) [Figs. 381, 382, 383] (in part)
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13b. Involucre with 1 series of monomorphic, herbaceous or subherbaceous bracts; pappus none
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14a. Leaves alternate; inner flowers of capitulum (i.e., the disk flowers) bisexual, with a bifid style; plants annual, 1–10 dm tall (in part)
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14b. Leaves opposite (the uppermost sometimes alternate); inner flowers of capitulum functionally unisexual, the ovary abortive and the style undivided; plants perennial or coarse annuals, 5–30 dm tall
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15a. Larger leaves with pinnately lobed and toothed blades [Fig. 445]; involucre 6–11 mm tall (in part)
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15b. Leaves with simple blades that are toothed or double toothed; involucre 1.5–4 mm tall
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16a. Capitulescence (or the principal branches in robust plants) raceme-like or spike-like; peduncles 0–3 mm long, many subtended by leaf-like bracts; carpellate flowers with a corolla 0.5–1 mm long
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16b. Capitulescence panicle-like; peduncles 1–6 (–12) mm long, few (if any) subtended by leaf-like bracts; carpellate flowers with a corolla 0.1–0.5 mm long, or the corolla absent
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4b. Receptacle without bristles or chaff (the persistent floral stipes of Cotula sometimes misinterpreted as chaff); corollas yellow (or usually blue to lavender in Ageratum or lacking in the carpellate flowers of Ambrosia trifida)
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17b. Leaves alternate or opposite; capitula usually more than one in the axils of leaves, at the tips of branches, and/or at the summit of the stem; terrestrial plants
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18a. Leaves opposite
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19a. Plants synoecious (i.e., with capitula that have bisexual flowers); pappus present; leaf blades simple to dissected, but none palmately lobed
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20a. Leaf blades dissected into narrow segments; pappus composed of 10–20 scales that are cleft into 5–10 bristles at the apex; inner involucral bracts rounded to obtuse at apex (in part)
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20b. Leaf blades simple merely toothed; pappus composed of (4–) 5 (–6) scales that are fringed along the margins and terminate in a single, long awn; involucral bracts narrowed to an awn-like point 0.5–2 mm long
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19a. Plants monoecious (i.e., with separate staminate and carpellate capitula); pappus absent; usually at least some leaf blades palmately lobed [Fig. 372] (in part)
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18b. Leaves alternate
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21a. Pappus of 2–8 firm, but deciduous, awns; involucral bracts squarrose and heavily resinous (in part)
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21b. Pappus of scales, a short crown, or none; involucral bracts neither squarrose nor resinous
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22a. Capitulescence a solitary capitulum at the tips of branches or in the axils of leaves; outermost series of flowers lacking a corolla;; low, procumbent or trailing herbs
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23a. Capitula at the tips of branches; inner flowers stipitate, the stipes persistent on the receptacle; leaf blades (10–) 20–30 (–70) mm long; cypselas with two evident ribs or wings
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23b. Capitula mainly in the axils of leaves; inner flowers not stipitate; leaf blades 5–15 mm long; cypselas with ridged but not winged
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22b. Capitulescence with multiple capitula, all the flowers with a corolla; none of the flowers stipitate; erect or ascending herbs or shrubs
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24b. Capitulescence resembling a corymb or cyme; pappus of scales or a short crown
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25a. Pappus of 4–10 scales, the longer scales 2–6 mm wide
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26a. Corolla lobes narrow-lanceolate to linear, mostly more than 2 times as long as wide; all corollas actinomorphic
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26b. Corolla lobes lanceolate to triangular, mostly 1–2 times as long as wide; outer corollas enlarged and zygomorphic
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25b. Pappus a short crown 0.2–0.4 mm long
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27a. Leaf blades toothed, sometimes with a few basal lobes as well; cypselas with 5–8 rib-like nerves (in part)
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27b. Leaf blades 1- to 3-times pinnatifid; cypselas with 5 or fewer rib-like nerves
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Show photos of:
Each photo represents one genus in this subgroup.