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Asteraceae Group 2
See list of 29 genera in this group-
1a. Leaf blades spiny-margined [Fig. 385]; involucral bracts (at least some of them) with a simple spine tip (the spine tip sometimes short in Cirsium muticum and C. palustre) [Fig. 390]; receptacle densely bristly setose between the disk flowers (except in Onopordum)
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2a. Leaf blades streaked or blotched with white; lower part of free portion of filaments connate into a tube; pappus dimorphic—an outer series of minutely barbellate, narrow (i.e. bristle-like) scales and an inner series of minute, smooth bristles
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2b. Leaf blades not streaked or blotched with white (though sometimes entirely or strongly suffused with white in Cirsium arvense); free portion of filaments distinct; pappus monomorphic, consisting of minutely barbellate or plumose bristles
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3a. Pappus bristles plumose (i.e., pinnately branched); stem and branches with or without prickly, decurrent wings
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3b. Pappus bristles minutely barbellate; upper stem and branches with conspicuous, prickly and undulate-margined wings formed by decurrent leaf bases
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4a. Receptacle flat, fleshy, deeply pitted with polygonal depressions that are dentate or short setose around the margins, lacking elongate bristles between the disk flowers; pappus pale red
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4b. Receptacle flat to conic, not fleshy, shallowly pitted, densely bristly setose between the disk flowers; pappus ± white
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1b. Leaf blades without spines; involucral bracts not spine-tipped (except Symphyotrichum ericoides) or the bracts with palmately or pinnately branched spines [Figs. 370,387,405]; receptacle lacking bristle-like setae (except Centaurea)
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5a. Receptacle densely bristly setose; most or all of the involucral bracts tipped with an erose or a fimbriate- to pectinate-fringed appendage, the appendage sometimes spinose (entire in Amberboa); cypselas attached laterally or obliquely to the receptacle
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6a. Apical appendage of the involucral bracts erose or fimbriate- to pectinate-fringed, the appendage sometimes spinose; cypsela body with an entire apex, lacking a conspicuous rim around the attachment scar; pappus absent or of minutely barbellate bristles (in part)
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6b. Apical appendage of the involucral bracts entire; cypsela body with a minutely denticulate apex, with a conspicuous rim around the attachment scar; pappus absent or of slender scales
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5b. Receptacle lacking bristle-like setae; involucral bracts with entire or ciliate margins; cypselas attached basally to the receptacle
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7a. Pappus double—an inner series of elongate, slender bristles and an outer series of short, scale-like bristles; style branches slender, gradually tapering to the apex, minutely pubescent on the outer surfaces
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7b. Pappus single, composed entirely of elongate, slender bristles (pappus double in Crupina, the inner series of black-brown bristles); style branches truncate, rounded, clavate-thickened, or shortly tapering to apex, mostly glabrous or minutely papillose, infrequently pubescent and then the hairs restricted to an apical tuft or an apical appendage
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8a. Plants pubescent with white or gray tomentum or sericeo-tomentum, at least on the abaxial leaf surface (often also on the stem; some species becoming glabrate late in growing season)
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9a. Stems resembling a scape, scaly bracteate, appearing before the leaves; foliage leaves all basal, 5–40 cm wide, palmately lobed (in part)
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9b. Stems resembling a scape or not, in either case appearing after the leaves; leaves basal or produced on a stem, 0.2–5.5 cm wide, entire
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10a. Plants dioecious or monoecious, none of the flowers bisexual (note: central flowers of carpellate Anaphalis appearing bisexual but have an undivided style with an abortive ovary and are functionally staminate)
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11a. Plants stoloniferous, with conspicuous rosettes of basal leaves, mostly 4–35 cm tall; staminate pappus apically clavate; carpellate pappus connate at the base and falling together; stems subscapose, with reduced, bract-like leaves
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11b. Plants not stoloniferous, without conspicuous rosettes of basal leaves, mostly 20–100 cm tall; pappus slender at the apex and distinct, falling separately; stems leafy, the leaf blades 7.5–12 cm long
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10b. Plants polygamous—the numerous outer flowers unisexual and carpellate, the few inner flowers bisexual
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12a. Receptacle with chaff; outer flowers of capitulum (i.e., the carpellate ones) without pappus
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13a. Chaff of carpellate flowers blunt at the apex, ± saccate, enclosing a disk flower; receptacle obovoid to abruptly expanded at the apex, 0.4–1.6 times as tall as wide; inner chaff spreading in fruit; cypselas dimorphic—the outer longer than the inner
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13b. Chaff of carpellate flowers acuminate to aristate at the apex, not saccate, enfolding (but not enclosing) a disk flower; receptacle clavate, 5–15 times as tall as wide; inner chaff erect to ascending in fruit; cypselas ± monomorphic
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12b. Receptacle without chaff; both the outer carpellate flowers and the inner bisexual flowers with pappus
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14a. Involucral bracts yellow-white to sordid white; capitulescence corymb-like, with elongate lower branches; outer disk flowers yellow when fresh
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14b. Involucral bracts light brown, yellow-brown, or green-brown to brown (sometimes pink to purple); capitulescence not corymb-like, either tall and slender (i.e., spike-like), subcapitate, or composed of axillary clusters [Figs. 413,415,440]; outer disk flowers purple or at least apically purple when fresh
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15a. Capitulescence composed of small axillary clusters of capitula [Fig. 415]; involucre 2–3 mm tall; axis of plant often profusely branched; pappus bristles distinct but joined at the base by short, interlocking cilia
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15b. Capitulescence spike-like or subcapitate, in either case terminal [Figs. 413,440]; involucre 3–7 mm tall; axis of plant simple to sparingly branched; pappus bristles either connate at the base into a ring or distinct and without interlocking cilia
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16a. Capitulescence consisting of a terminal cluster of capitula 10–15 mm in diameter, subtended by 3–5 leaf-like bracts, sometimes also with some smaller axillary clusters; stem leaves subclasping, with revolute margins
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16b. Capitulescence spike-like, tall and slender (subcapitate in depauperate plants), the axillary capitula subtended by a solitary leaf-like bract; stem leaves not clasping, with ± plane margins
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17a. Body of cypsela glabrous; involucre 3–5 mm tall; pappus bristles basally connate into a ring, the entire set falling as a unit; body of cypsela 0.4–0.9 mm long; plants annual or biennial, of low elevations
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17b. Body of cypsela sparsely strigose; involucre 5–7 mm tall; pappus bristles basally connate or not; body of cypsela 1–1.5 mm long; plants perennial, boreal or alpine
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8b. Plants glabrous or pubescent, but not conspicuously tomentose
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18a. Leaves opposite or whorled (those of the upper stem sometimes alternate) [Fig. 433]
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19a. Plants vines; involucre with 4 principal bracts
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19b. Plants herbs; involucre with more than 4 principal bracts
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20a. Leaves both opposite and borne on distinct petioles (rarely the upper leaves sessile)
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21a. Involucral bracts all of similar length (1 or 2 outer, very small bracts may also be present) [Fig. 370]; pappus bristles tapering to a fine point; adaxial (i.e., inner) surface of corolla lobes papillose (i.e., with a layer of projecting cells)
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21b. Involucral bracts of (2–) 3 or more conspicuously different lengths; pappus bristles blunt at the apex; adaxial surface of corolla lobes smooth (in part)
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20b. Leaves opposite and ± sessile (i.e., the petioles, if present, ill defined), or whorled
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22a. Leaves in whorls of 3–7 with blades (15–) 20–150 (–180) mm wide; corollas, and often also the involucral bracts, pink to purple; involucres usually cylindric in flower, the margins parallel or slightly upwardly flared
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22b. Leaves usually opposite with blades 0.5–40 (–60) mm wide (whorled in E. hyssopifolium and E. torreyanum, but then with blades only 0.5–10 (–17) mm wide); corollas white (pink to purple in rare forms of E. perfoliatum); involucral bracts variously colored, usually with green and white, but not pink to purple; involucres usually with a distinct upward flare in flower, obviously narrower near base compared with apex (in part)
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18b. Leaves alternate throughout the stem
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23a. Capitulum with 3–5 flowers, usually only the inner 1 fertile and producing fruit; pappus of fertile flowers double—an outer series of short, triangular-lanceolate scales and an inner series of elongate, black-brown bristles
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23b. Capitulum with 5 or more flowers, producing more than 1 fruit; pappus single, all of elongate bristles, white to brown or purple
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24a. Capitula 3–5 cm in diameter, with 200–450 disk flowers; involucre 10–20 mm long, with bracts that spread from the base during flowering (these becoming deflexed during fruiting
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24b. Capitula narrower than 3 cm, with (4–) 6–110 florets; involucre 4–17 mm long,
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25a. Plants woody, often scurfy-pubescent on the capitulescence branches and involucral bracts, dioecious—the carpellate plants with capitula containing only slender, tubular corollas lacking apical teeth, the staminate plants with apically 5-lobed corollas and abortive ovaries with frequently connate style branches
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25b. Plants herbaceous, glabrous or pubescent but not scurfy, either synoecious and with all of the disk corollas of the capitulum with apical lobes or polygamous and then with unlobed, tubular corollas near the periphery and apically lobed corollas near the center of the capitulum
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26a. All flowers of the capitula bisexual; plants perennial, or annual in most Senecio
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27a. Corollas red-purple (rarely white); capitulescence tall and slender, resembling a raceme; involucre consisting of 3 or more series of bracts of distinctly unequal lengths [Fig. 431]
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27b. Corollas yellow to orange or green-white to yellow-white (rarely pink-tinged); capitulescence resembling a panicle or corymb; involucre consisting of a single series of long bracts, sometimes calyculate as well [Fig. 449] (in part)
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26b. At least the marginal flowers of the capitula unisexual and carpellate; plants annual
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28a. Involucre evidently pubescent with short, multicelled, glandular-viscid hairs, arranged in several, overlapping series of dissimilar length bracts, commonly tinged with anthocyanin; anthers filiform-tailed
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28b. Involucre not glandular-pubescent, in 1 or more series of long, ± equal length bracts (sometimes with a very short, outer series of bracts in Erechtites), green; anthers cuneate to sagittate at the base, but not tailed
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29a. Involucre 10–15 mm tall, in 1 series of long, nearly equal length bracts, sometimes calyculate, turbinate-cylindric, conspicuously swollen at the base before anthesis [Fig. 399]; leaf blades sharply serrate and sometimes also irregularly lobed; cypsela body 2–5.5 mm long
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29b. Involucre 5–11 mm tall, in 3 or 4 series of nearly equal length bracts, without a basal swelling; leaf blades entire; cypsela body up to 2 (–2.2) mm long (in part)
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Each photo represents one genus in this subgroup.