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FNA | Family List | FNA Vol. 20 | Asteraceae

187k. Asteraceae Martinov tribe Astereae Cassini, J. Phys. Chim. Hist. Nat. Arts. 88: 195. 1819.

Annuals, biennials, perennials, subshrubs, shrubs, or trees. Leaves usually cauline, sometimes mostly basal; alternate [opposite, whorled]; usually petiolate, sometimes sessile; margins entire or dentate to pinnatifid (often gland-dotted, especially in xerophytes). Heads homogamous (discoid; unisexual in Baccharis) or heterogamous (disciform or radiate), usually in corymbiform, paniculiform, racemiform, or spiciform arrays, sometimes borne singly. Calyculi 0. Phyllaries persistent or falling, usually in 3–5+ series (usually in spirals, sometimes in vertical ranks), distinct, unequal, and herbaceous to chartaceous or scarious or margins and/or apices notably scarious, sometimes in 1–2 series, distinct, subequal, and herbaceous with margins and/or apices barely to notably scarious. Receptacles usually flat to conic, sometimes concave, usually epaleate, rarely paleate (often foveolate, socket margins often fimbrillate; paleate in Eastwoodia and Rigiopappus). Ray florets 0 or in 1(–2+) series, usually pistillate, rarely neuter or styliferous and sterile; corollas usually yellow, cyanic, or white (laminae sometimes very reduced, e.g., Conyza spp.). Peripheral (pistillate) florets 0 or (in disciform heads) in 1–3+ series; corollas usually present, usually yellow, sometimes white, ochroleucous, or reddish to cyanic. Disc (inner) florets usually bisexual and fertile, rarely functionally staminate (e.g., Benitoa); corollas usually yellow, sometimes white, ochroleucous, or cyanic, actinomorphic, not 2-lipped, lobes (4–)5; anther bases obtuse or rounded, not tailed, apical appendages usually triangular to linear, sometimes none; styles abaxially glabrous and smooth or papillate (distally), branches ± linear, adaxially stigmatic in 2 lines from bases to apices or appendages, appendages usually deltate to lanceolate (abaxially papillate to hispidulous, adaxially smooth, glabrous). Cypselae monomorphic or dimorphic within heads, usually ± columnar to prismatic and 5-ribbed, sometimes compressed and 2-ribbed, rarely beaked, bodies smooth, muricate, ribbed, or rugulose (glabrous or hairy, hairs often glandular); pappi (rarely 0) usually persistent, usually of barbellulate to barbellate bristles in (1–)2–3+ series, sometimes of scales (scales sometimes aristate), rarely of both scales and bristles or of awns.

Genera 170, species 2800+ (77 genera, 719 species in the flora): almost worldwide, mostly temperate.

The classification and phylogeny of tribe Astereae has been the object of recent work, both morphologic (K. Bremer 1994; G. L. Nesom 1994, 2000) and molecular (notably the seminal paper by R. D. Noyes and L. H. Rieseberg 1999). Noyes and Rieseberg showed that most genera present in North America belong to a single monophyletic clade, called the North American clade. A series of subsequent studies done in various generic groups or subtribes led to a redefinition of many genera (see literature cited in each genus) and to the transfer of species between genera. The current treatment of the tribe reflects much of these novelties, many presented in a floristic work for the first time. Nesom and H. Robinson (unpubl.) present a worldwide overview of the classification of the tribe.

Large genera such as Erigeron, Symphyotrichum, and Solidago all originated on the continent and subsequently spread to Eurasia or South America. A few genera entered North America from neighboring continents, such as Aster in the strict sense (from Eurasia) or Baccharis (from Central America). A majority of Astereae genera in the flora of North America are endemic to the continent (more so if Mexico were included).

The generic order of the present treatment attempts to reflect the phylogenetic relationships established in recent molecular phylogenetic work.


Anderson, L. C. and J. B. Creech. 1975. Comparative leaf anatomy of Solidago and related Asteraceae. Amer. J. Bot. 62: 486–493. Beck, J. B. et al. 2004. Is subtribe Solidagininae (Asteraceae) monophyletic? Taxon 53: 691–698. Brouillet, L., L. E. Urbatsch, and R. P. Roberts. 2004. Tonestus kingii and T. aberrans are related to Eurybia and the Machaerantherinae (Asteraceae: Astereae) based on nrDNA (ITS and ETS) data: Reinstatement of Herrickia and a new genus, Triniteurybia. Sida 21: 889–900. Cronquist, A. and D. D. Keck. 1957. A reconstitution of the genus Machaeranthera. Brittonia 9: 231–239. Fiz, O., V. Valcárcel, and P. Vargas. 2002. Phylogenetic position of Mediterranean Astereae and character evolution of daisies (Bellis, Asteraceae) inferred from nrDNA ITS sequences. Molec. Phylogen. Evol. 25: 157–171. Hall, H. M. 1928. The genus Haplopappus: A phylogenetic study in the Compositae. Publ. Carnegie Inst. Wash. 389. Hartman, R. L. 1976. A Conspectus of Machaeranthera (Compositae: Astereae) and a Biosystematic Study of the Section Blepharodon. Ph.D. dissertation. University of Texas. Hartman, R. L. 1990. A conspectus of Machaeranthera (Asteraceae: Astereae). Phytologia 68: 439–465. Jones, A. G. 1980. A classification of New World species of Aster (Asteraceae). Brittonia 32: 230–239. Jones, A. G. and D. A. Young. 1983. Generic concepts of Aster (Asteraceae): A comparison of cladistic, phenetic and cytological approaches. Syst. Bot. 8: 71–84. Kapoor, B. M. and J. R. Beaudry. 1966. Studies on Solidago. VII. The taxonomic status of the taxa Brachychaeta, Brintonia, Chrysoma, Euthamia, Oligoneuron, and Petradoria in relation to Solidago. Canad. J. Genet. Cytol. 8: 422–443. Lane, M. A. 1982. Generic limits of Xanthocephalum, Gutierrezia, Amphiachyris, Gymnosperma, Greenella, and Thurovia. (Compositae: Astereae). Syst. Bot. 7: 405–416. Lane, M. A. et al. 1996. Relationships of North American genera of Astereae, based on chloroplast DNA restriction site data. In: D. J. N. Hind et al., eds. 1996. Proceedings of the International Compositae Conference, Kew, 1994. 2 vols. Kew. Vol. 1, pp. 49–77. Morgan, D. R. 1997. Reticulate evolution in Machaeranthera (Asteraceae). Syst. Bot. 22: 599–615. Morgan, D. R. 2003. nrDNA external transcribed spacer (ETS) sequence data, reticulate evolution, and the systematics of Machaeranthera (Asteraceae). Syst. Bot. 28: 179–190. Morgan, D. R. and R. L. Hartman. 2003. A synopsis of Machaeranthera (Asteraceae: Astereae), with recognition of segregate genera. Sida 20: 1837–1416. Morgan, D. R. and B. B. Simpson. 1992. A systematic study of Machaeranthera (Asteraceae) and related groups using restriction site analysis of chloroplast DNA. Syst. Bot. 17: 511–531. Nesom, G. L. 1991b. A phylogenetic hypothesis for the goldenasters (Asteraceae: Astereae). Phytologia 71: 136–151. Nesom, G. L. 1993b. Taxonomic infrastructure of Solidago and Oligoneuron (Asteraceae: Astereae) and observations on their phylogenetic position. Phytologia 75: 1–44. Nesom, G. L. 1994. Subtribal classification of the Astereae (Asteraceae). Phytologia 76: 193–274. Nesom, G. L. 1994b. Review of the taxonomy of Aster sensu lato (Asteraceae: Astereae), emphasizing the New World species. Phytologia 77: 141–297. Nesom, G. L. 1997. Taxonomic adjustments in North American Aster sensu latissimo (Asteraceae: Astereae). Phytologia 82: 281–288. Nesom, G. L. 2000. Generic Conspectus of the Tribe Astereae (Asteraceae) in North America, Central America, the Antilles, and Hawaii. Fort Worth. [Sida Bot. Misc. 20.] Noyes, R. D. 2000. Biogeographical and evolutionary insights on Erigeron and allies (Asteraceae) from ITS sequence data. Pl. Syst. Evol. 220: 93–114. Noyes, R. D. and L. H. Rieseberg. 1999. ITS sequence data support a single origin for North American Astereae (Asteraceae) and reflect deep geographic divisions in Aster s.l. Amer. J. Bot. 86: 398–412. Ruffin, J. 1974. A taxonomic evaluation of the genera Amphiachyris, Amphipappus, Greenella, Gutierrezia, Gymnosperma, Thurovia, and Xanthocephalum (Compositae). Sida 5: 301–333. Ruffin, J. 1977. Palynological survey of the genera Amphiachyris, Amphipappus, Greenella, Gutierrezia, Gymnosperma, and Xanthocephalum (Compositae). Contr. Gray Herb. 207: 117–131. Semple, J. C. and L. Brouillet. 1980. A synopsis of North American asters: The subgenera, sections and subsections of Aster and Lasallea. Amer. J. Bot. 67: 1010–1026. Semple, J. C., S. B. Heard, and L. Brouillet. 2002. Cultivated and Native Asters of Ontario (Compositae: Astereae). Aster L. (Including Asteromoea Blume, Diplactis Raf. and Kalimeris (Cass.) Cass.), Callistephus Cass., Galatella Cass., Doellingeria Nees, Oclemena E. L. Greene, Eurybia (Cass.) S. F. Gray, Canadanthus Nesom, and Symphyotrichum Nees (Including Virgulus Raf.). Waterloo. [Univ. Waterloo Biol. Ser. 41.] Semple, J. C. and J. L. A. Hood. 2005. Pappus variation in North American Asters. I. Double, triple and quadruple pappus in Symphyotrichum and related aster genera (Asteraceae: Astereae). Sida 21: 2141–2159. Semple, J. C., G. S. Ringius, and J. J. Zhang. 1999. The Goldenrods of Ontario: Solidago L. and Euthamia Nutt., ed. 3. Waterloo. [Univ. Waterloo Biol. Ser. 39.] Semple, J. C. and L. Tebby. 1999. A cladistic analysis of subtribe Chrysopsidinae (Asteraceae: Astereae). In: International Botanical Congress. [1999.] Abstracts. XVI International Botanical Congress, St. Louis, USA, August 1–7, 1999. [St. Louis.] Abstr. 2852, poster 401. Solbrig, O. T. 1960. The status of the genera Amphiachyris, Amphipappus, Greenella, Gutierrezia, Gymnosperma, and Xanthocephalum (Compositae). Rhodora 62: 43–53. Suh, Y. and B. B. Simpson. 1990. Phylogenetic analysis of chloroplast DNA in North American Gutierrezia and related genera (Asteraceae: Astereae). Syst. Bot. 660–670. Turner, B. L. 1987b. Taxonomic study of Machaeranthera, sections Machaeranthera and Hesperastrum (Asteraceae). Phytologia 62: 207–266. Urbatsch, L. E., R. P. Roberts, and V. Karaman. 2003. Phylogenetic evaluation of Xylothamia, Gundlachia, and related genera (Asteraceae, Astereae) based on ETS and ITS nrDNA sequence data. Amer. J. Bot. 90: 634–649. Xiang, C. and J. C. Semple. 1996. Molecular systematic study of Aster sensu lato and related genera (Asteraceae: Astereae) based on chloroplast DNA restriction site analyses and mainly North American taxa. In: D. J. N. Hind et al., eds. 1996. Proceedings of the International Compositae Conference, Kew, 1994. 2 vols. Kew. Vol. 1, pp. 393–423. Zanowiak, D. J. 1991. An Analysis of Systematic and Phyletic Relationships within Baccharidinae (Asteraceae: Astereae). Ph.D. dissertation. Texas A&M University. Zhang, J. J. 1996. A Molecular Biosystematic Study on North American Solidago and Related Genera (Asteraceae: Astereae) Based on Chloroplast DNA RFLP Analysis (Phylogenetics). Ph.D. dissertation. University of Waterloo.

Key B Annuals or biennials

1 Heads discoid or disciform (sometimes radiant)   (2)
+ Heads radiate   (11)
2 (1) Heads discoid   (3)
+ Heads disciform   (7)
3 (2) Pappi of (1–)2–10 setiform to subulate scales   (4)
+ Pappi 0, or of 3–55 bristles   (5)
4 (3) Plants eglandular; heads sessile or subsessile, in secund, spiciform arrays   153 Thurovia (in part), p. 86
+ Plants usually gland-dotted and/or vernicose; heads usually in corymbiform arrays, rarely borne singly   202 Grindelia (in part), p. 424
5 (3) Plants (gracile) 2–14 cm; leaves (linear to filiform) entire; pappi 0, or of (3–)5 bristles or setiform scales   145 Pentachaeta (in part), p. 46
+ Plants (1–)2–100 cm; leaves entire, toothed, or pinnately lobed; pappi of 3–55 bristles   (6)
6 (5) Leaf adaxial faces glabrous, puberulent, or canescent; involucres turbinate; phyllaries usually spreading to reflexed, rarely appressed; corollas yellow (limbs of peripheral florets not expanded); pappus bristles white to tawny, distinct   197 Dieteria (in part), p. 395
+ Leaf adaxial faces sparsely tomentose to woolly; involucres hemispheric, obconic, campanulate, or narrowly cylindric; phyllaries erect or recurved; corollas white, pink, lavender, or yellow (limbs of peripheral florets freqently palmately expanded, heads ± radiant); pappus bristles tan to reddish, distinct or connate   209 Lessingia, p. 452
7 (2) Annuals (eglandular); disc corollas without prominent orange veins, style appendages lanceolate or linear   (8)
+ Biennials or annuals (usually gland-dotted or stipitate-glandular, sometimes eglandular, in Conyza); disc corollas sometimes with prominent orange veins (Conyza, Erigeron), style appendages deltate   (9)
8 (7) Heads borne singly; peripheral pistillate (or reduced ray) florets in 1 series; pappi 0, or of (3–)5 bristles or subulate scales (not surpassing corollas at flow-ering); grassy areas, chaparral, California   145 Pentachaeta (in part), p. 46
+ Heads in paniculiform arrays (borne singly in small plants); peripheral pistillate florets in 2+ series; pappi of (20–)25–40(–55) bristles (surpassing corollas at flowering); ± saline habitats, edges of ponds, irrigation ditches, salted road-sides, saltmarshes; Rocky Mountains eastward   214 Symphyotrichum (in part), p. 465
9 (7) Biennials; stems ascending; heads borne singly (at ends of branches), disc corolla throats somewhat inflated, white-indurate; pappi of outer, shorter setae plus 15–20 inner, barbellate bristles   186 Erigeron (in part), p. 256
+ Annuals; stems erect; heads usually in corymbiform, paniculiform or racemiform arrays, rarely borne singly; disc corollas narrowly funnelform (throats neither inflated nor indurate); pappi of 10–30 barbellate bristles   (10)
10 (9) Leaf faces often stipitate-glandular or gland-dotted; phyllaries lacking orange to brown midnerves; cypselae densely sericeous, ± strigillose, or glabrous, often stipitate-glandular and/or gland-dotted   142 Laënnecia (in part), p. 36
+ Leaf faces eglandular; phyllaries with orange to brownish midnerves; cypselae glabrous or strigillose, eglandular   187 Conyza (in part), p. 348
11 (1) Rays usually yellow or orange, sometimes cream, whitish, or white   (12)
+ Rays white, pink, purple, or blue   (25)
12 (11) Pappi usually 0, or coroniform, or of scales, rarely of relatively short bristles (Xanthocephalum)   (13)
+ Pappi of bristles, or of outer, shorter setae or scales plus inner, longer bristles, or of outer bristles plus inner, subulate to setiform scales   (17)
13 (12) Stems and leaves eglandular; phyllaries subequal (± navicular, inner usually each ± enfolding floret); receptacles sparsely paleate between ray and disc florets (paleae resembling phyllaries); ray corollas yellowish, often tinged with red or purple (laminae inconspicuous); disc corolla lobes 2–4   146 Rigiopappus, p. 48
+ Stems and leaves (at least partly) stipitate-glandular; phyllaries unequal (not navicular nor each enfolding floret); receptacles epaleate; ray corollas yellow to orange-yellow or occasionally suffused with red (laminae conspicuous); disc corolla lobes 5   (14)
14 (13) Disc corollas abruptly ampliate, throats usually campanulate, sometimes funnelform   (15)
+ Disc corollas not abruptly ampliate, throats funnelform or cylindric   (16)
15 (14) Cypselae terete or slightly compressed with rounded edges or 4–6-sided, without prominent nerves, glabrous or slightly strigose; pappi of rays 0, outer discs 0 or minute crowns, inner 0, or usually of scales, rarely bristles; Arizona, Texas   203 Xanthocephalum, p. 436
+ Cypselae ± triquetrous, 3-nerved, sericeous; pappi of 2–8 subulate, barbellate scales; California   207 Benitoa, p. 450
16 (14) Leaves not glutinous; heads in paniculiform or corymbiform arrays; phyllaries glutinous; disc florets functionally staminate   154 Amphiachyris, p. 87
+ Leaves glutinous; heads borne singly or in clusters of 3–6; phyllaries not glutinous; disc florets bisexual, fertile   155 Gutierrezia (in part), p. 88
17 (12) Stems and leaves usually gland-dotted and/or resinous; involucres usually globose to hemispheric or broadly urceolate, sometimes campanulate or obconic; phyllaries hooked, looped, patent, recurved, straight, or incurved   202 Grindelia (in part), p. 424
+ Stems and leaves usually not resinous, sometimes gland-dotted or stipitate-glandular; involucres hemispheric, campanulate, turbinate, obconic, or cylindric; phyllaries appressed, spreading, reflexed, or recurved   (18)
18 (17) Cypselae dimorphic (rays often ± 3-angled, discs ± compressed)   (19)
+ Cypselae monomorphic (all ± compressed or all ± 3-angled)   (21)
19 (18) Biennials; stems strigose and/or hispid, stipitate-glandular; pappi of rays 0, of discs of outer scales plus 30–45 inner bristles   185 Heterotheca (in part), p. 230
+ Annuals or biennials; stems glabrous or hispid, gland-dotted or stipitate-glandular; pappi of basally flattened bristles (or setiform scales) in 2–4 series   (20)
20 (19) Heads borne singly or in corymbiform arrays (peduncles not cobwebby); involucres 4–10 mm; disc corolla throats gradually ampliate, ± funnelform; style-branch appendages lanceolate   195 Xanthisma (in part), p. 383
+ Heads borne singly or (2–3) in paniculiform or subcorymbiform-cymiform arrays (peduncles often cobwebby); involucres 7–16 mm; disc corolla throats abruptly ampliate, funnelform; style-branch appendages deltate   204 Rayjacksonia (in part), p. 437
21 (18) Stems glabrous or glabrate, eglandular; cauline leaves narrowly oblanceolate, linear, or filiform, margins entire, ciliate, faces glabrous or glabrate, eglandular; heads borne singly (at ends of branches); phyllaries not thickened or keeled; rays yellow and often reddish or purplish-tinged   (22)
+ Stems ± hispid, pilose, woolly or arachnose, sometimes glabrous, stipitate-glandular or eglandular; cauline leaves ovate, oblanceolate, elliptic, lanceolate, or linear, margins entire, serrate, or apically dentate, sometimes coarsely ciliate, faces usually hairy, sometimes glabrous, sometimes stipitate-glandular; heads borne singly or in corymbiform, subumbelliform, or paniculiform arrays; phyllaries thickened or keeled; ray florets yellow to yellow-orange   (23)
22 (21) Involucres campanulate to turbinate; phyllaries equal or subequal; cypselae oblanceoloid, 3–5-nerved, not beaked; pappus bristles (3–)5–20 (usually in multiples of 5) in 1 series   145 Pentachaeta (in part), p. 46
+ Involucres ± cylindric to turbinate or obconic; phyllaries unequal; cypselae ± fusifom, 5-nerved, beaked; pappus bristles (12–)30–40 in (1–)2 series (outer shorter)   147 Tracyina, p. 50
23 (21) Biennials, stems arachnose to woolly or glabrous, often stipitate-glandular; heads in corymbiform, subumbelliform, or paniculiform arrays; pappus bristles relatively fine (mainly Florida, Atlantic coastal plain)   182 Chrysopsis (in part), p. 213
+ Annuals, stems sparsely hispid or pilose, sometimes stipitate-glandular; heads borne singly or in loose paniculiform arrays; pappus bristles relatively thick and rigid, outer sometimes scalelike   (24)
24 (23) Leaves 1-nerved, faces hispido-pilose; involucres campanulate, 6–9 mm; phyllaries linear, sparsely stipitate-glandular; cypselae obconic, compressed, smooth or slightly ribbed; Gulf coastal plain, Mississippi embayment, adjacent lowlands   181 Bradburia (in part), p. 211
+ Leaves 3-nerved (nerves ± parallel), faces thin-arachnose (in minute, abaxial lacunae); involucres narrowly turbinate to subcylindric, 4–8 mm; phyllaries lanceolate to linear-lanceolate, eglandular; cypselae turbinate, terete to weakly angled, 6–14-nerved; sc United States, adjacent Mexico   184 Croptilon (in part), p. 228
25 (11) Receptacles conic; pappi 0, or coroniform, or of scales   (26)
+ Receptacles flat to convex; pappi usually of bristles (sometimes only discs or rays), or of setiform scales, or of bristles plus scales, or toothed cups with 1 bristle, sometimes of scales, or coroniform, or 0   (30)
26 (25) Leaves usually pinnatifid to dentate, sometimes entire; rays without midstripe abaxially; cypselae not or slightly compressed, glabrous or sparsely strigose (hairs not glochidiform); pappi cartilaginous crowns, or crowns of scales or setae, or 0   (27)
+ Leaves usually entire, sometimes dentate or lobed; rays usually with pink or purplish midstripe abaxially; cypselae strongly compressed or flattened, glabrous or hairy (hairs glochidiform); pappi usually of awns, scales, bristles, or 2-horned crowns, sometimes 0   (28)
27 (26) Plants gland-dotted; cypselae oblong to narrowly obovoid, slightly compressed, 2-nerved, sometimes gland-dotted   141 Egletes, p. 35
+ Plants eglandular; cypselae columnar to prismatic, usually 4-angled, 4–12-ribbed (ribs relatively thick), eglandular   188 Aphanostephus (in part), p. 351
28 (26) Phyllaries in 4–6+ series, unequal; pappi of 12–35+ lanceolate or subulate to setiform scales   176 Townsendia (in part), p. 193
+ Phyllaries in 2(–3) series, subequal; pappi 0, or crowns of setae or scales, or of 2 long plus ring of shorter awns   (29)
29 (28) Leaves spatulate-obovate (basal), narrower distally; cypsela margins ribbed; pappi 0, or crowns of setae or scales   177 Astranthium (in part), p. 203
+ Leaves oblanceolate; cypsela margins winglike; pappi of 2 long plususually ring of shorter awns   178 Dichaetophora, p. 205
30 (25) Disc corollas with orange-resinous veins   (31)
+ Disc corolla veins not orange-resinous   (34)
31 (30) Heads borne singly; pappi crowns (sometimes each with 1 bristle) or of alternating scales and bristles   (32)
+ Heads usually in corymbiform or paniculiform arrays, sometimes borne singly; pappi of bristles, or of outer, shorter setae or scales plus inner, longer bristles   (33)
32 (31) Phyllaries in 2–6 series, unequal; pappi hyaline crowns (nearly 0) oralternating bristles and scales   179 Chaetopappa (in part), p. 206
+ Phyllaries in 1(–2) series, equal; pappi toothed crowns plus 1 distallyplumose bristle, or of 1–12 bristles alternating with scales   180 Monoptilon, p. 210
33 (31) Disc corolla throats slightly indurate and inflated; pappi usually of outer setae or scales plus 10–30 inner bristles, sometimes 0   186 Erigeron (in part), p. 256
+ Disc corolla throats not indurate or inflated; pappi of 15–25+ bristles in 1 series   187 Conyza (in part), p. 348
34 (30) Pappi of 12–35+ scales   176 Townsendia (in part), p. 193
+ Pappi of 5–80+ bristles or setiform scales   (35)
35 (34) Pappus bristles usually 5, rarely 0   145 Pentachaeta (in part), p. 46
+ Pappus bristles or setiform scales usually 20–80+ (ray sometimes 0)   (36)
36 (35) Stems glabrous or hairy in lines distally, sometimes stipitate-glandular distally; leaf margins entire, subserrate, serrate, or pinnately lobed; heads usually in paniculiform or corymbiform arrays, sometimes borne singly   (37)
+ Stems hairy or glabrous, sometimes stipitate-glandular; leaf margins entire, serrate, dentate, laciniate, lobed, or ± deeply 1–2-pinnatifid (teeth or lobes apiculate, bristly, or spiny); heads borne singly (at ends of branches) or in cymiform or corymbiform arrays   (38)
37 (36) Stems distally stipitate-glandular; cauline leaf bases clasping to subclasping, margins entire, coarsely toothed, or pinnately lobed, faces appressed-hairy or glabrous (distal stipitate-glandular); heads in corymbiform arrays; involucres broadly turbinate to hemispheric; phyllaries herbaceous distally, stipitate-glandular; ray florets 20–70 in 1 series, corollas white, blue, or purple; pappi: rays 0, discs of bristles   213 Psilactis, p. 462
+ Stems eglandular; cauline leaf bases attenuate, cuneate, or rounded, margins entire or serrulate, faces glabrous, eglandular; heads in paniculiform arrays; involucres cylindro-campanulate, cylindric, or turbinate; phyllaries with distinct green zones distally, eglandular; ray florets 16–54 in 1–3 series, or 90–110 in 4–5 series, corollas white, pink, or lavender; pappi of bristles   214 Symphyotrichum (in part), p. 465
38 (36) Leaves deeply 1–2-pinnatifid, at least many lobes or teeth acute and bristly   196 Machaeranthera, p. 394
+ Leaves entire or toothed or lobed, if 1–2-pinnatifid, teeth or lobes often rounded, sometimes apiculate, mostly not bristly   (39)
39 (38) Plants hairy, sometimes stipitate-glandular; leaves entire or toothed; ray pappi of 40–50 bristles   197 Dieteria (in part), p. 395
+ Plants glabrous and leaves entire or toothed (ciliate or teeth bristle-tipped or apiculate), or plants hairy, sometimes stipitate-glandular, and leaves 1–2-pinnatifid; ray pappi usually 0 (if 20–30 bristles, leaves 1–2-pinnatifid)   198 Arida (in part), p. 401

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