Description:

• Annual, biennial or perennial herbs, subshrubs, shrubs, occasionally scramblers or lianes, sometimes trees, rarely aquatic or epiphytic, sometimes succulent, sometimes spinescent, rarely monoecious or dioecious; typically with resin ducts or latex canals (tribe Lactuceae)
• Leaves alternate or opposite, sometimes whorled, or radical and rosulate, sessile or petiolate, usually simple, entire or toothed, lobed or variously dissected, glabrous or pubescent and/or glandular; stipules 0 but stipuliform appendages sometimes present
• Inflorescence a capitulum (or head) with 1-many individual flowers (florets) ± sessile and aggregated on a common receptacle and surrounded by an involucre of 1-many rows of bracts, often resembling a single flower; capitula solitary and terminal on scapes or leafy stems, or few to very many in lax or ± clustered corymbose or paniculate synflorescences, sometimes cymose, spicate, racemose or aggregated into secondary capitula or glomerules
• Receptacle flat, hemispherical or conical, with scales or setae subtending florets (paleate), or epaleate and surface smooth, areolate or shallowly to deeply honeycombed (alveolate); alveolae often fimbriate or setose
• Involucral bracts (phyllaries) in 2-many rows, free and imbricate or ± connate, or sometimes in 1 row and united or with cohering overlapping margins, persistent or rarely caducous, occasionally accrescent, sometimes apically appendaged; thickened region in lower part of bracts referred to as stereome; sometimes additional outer row of smaller bracts (calyculus) present (e.g. in Senecio)
• Florets epigynous, small, 1-500 or more per capitulum, bisexual, unisexual or sterile, regular or irregular
  • Two types of regular florets (nos.1-2):
    • (1) disc or central florets: tubular, with (3)4 or 5 apical lobes, bisexual, or functionally male or unisexual
    • (2) tubular-filiform (outer) florets: tube slender (anthers absent) with 2 or 3 small apical lobes, female
  • Four main types of irregular florets (nos. 3-6):
    • (3) bilabiate disc florets: ± tubular below, bilabiate above, with 3 outer and 2 inner lobes, mostly bisexual, rarely functionally male or female, situated on disc/central part of capitulum
    • (4) bilabiate ray florets: ± tubular below, bilabiate above with 2 small inner lobes and a 3-lobed, short to long, strap-shaped lamina, mostly female, rarely bisexual, situated on periphery of capitulum
    • (5) true ray florets: lamina strap-shaped with 3(4) apical lobes, inner lobes absent, usually female or neuter
    • (6) ligulate florets (ligules): lamina strap-shaped with 5 apical lobes, mostly bisexual (tribe Lactuceae), rarely female or male
  • (Note: all florets on the periphery of the receptacle, regardless of their morphology, are often referred to as marginal, outer or female florets, those occurring on the receptacle/disc, as disc or central florets)
• Capitula may be grouped into two broad categories:
  • Heterogamous capitula containing florets with different sex arrangements (e.g. female and bisexual)
  • Homogamous capitula containing florets with similar sex arrangements (mostly either bisexual or unisexual)
  • Further groupings are as follows:
    • Radiate capitula are usually heterogamous, containing bilabiate ray florets (no. 4) or true ray florets (no. 5) on periphery (mostly in 1 row) and central disc florets (no. 1) or bilabiate disc florets (no. 3)
    • Disciform capitula are usually heterogamous with at least two types of nonradiating florets, usually tubular-filiform outer florets (no. 2), in 1 or more rows, and central disc florets (no. 1)
    • Discoid capitula are usually homogamous containing only disc florets (no. 1)
    • Ligulate capitula are homogamous, containing only ligulate florets (no. 6), as in the tribe Lactuceae
  • Whether capitula are heterogamous or homogamous can be deduced from the description of the florets
• Calyx, if present, represented by a pappus consisting of persistent or caducous, 1-many-seriate hairs, bristles, awns or scales, or pappus elements ± fused to form annular or ± cup-shaped or ear-shaped corona borne apically on ovary/fruit; pappus setae scabrid, barbellate or ± plumose
• Corolla usually gamopetalous, of (3-)5 ± united petals, rarely 0
• Stamens (3-)5; filaments free, arising on corolla tube, contractile; anthers introrse, usually apically appendaged, usually laterally connate into a cylinder around style, thecae rounded, sagittate (tailed/caudate) and/or calcarate at base; pollen usually echinate, sometimes echinolophate or lophate
• Style of bisexual or functionally male florets elongating within anther tube, shallowly to deeply bifid, occasionally undivided in functionally male florets; style branches with stigmatic areas on inner sides, apex acute, rounded or truncate, or branches produced beyond stigmatic surfaces as triangular, subulate or clavate appendages, variously papillate or hairy, usually with brush of collecting hairs that sweep pollen from anther tube; style of female florets simpler, with acute to rounded style branches and without sweeping hairs
• Ovary inferior, of 2 united carpels, unilocular with 1 erect basal ovule
• Fruit unilocular, 1-seeded, indehiscent (a cypsela/achene), very rarely fleshy with single seed enclosed in hard endocarp (drupe) (Chrysanthemoides), sometimes produced apically into a beak (rostrum), crowned by persistent or caducous pappus, or epappose; endosperm 0 or vestigial

Nomenclature:

• Asteraceae:
  • Dumort.: 55 (1822) alternative name
  • Merxmüller: 1 (1967a)
  • Bremer: 13 (1994).
• Compositae:
  • Giseke: 538 (1792) name conserved
  • Harvey: 44 (1865)
  • Hilliard: 1 (1977)
  • Pope: 1 (1992)
• Cichoriaceae Juss.
  • Merxmüller: 1 (1967b)

Distribution & Notes:

• Global: Genera ± 1535 and 25000 species; cosmopolitan, absent only from Antarctica
• Southern Africa: Genera 246, species 2305

References:

• ANDERBERG, A.A. 1989. Phylogeny and reclassification of the tribe Inuleae (Asteraceae). Canadian Journal of Botany 67
• BREMER, K. 1994. Asteraceae, cladistics & classification. Timber Press, Portland, Oregon
• DUMORTIER, B.C.J. 1822. In Commentationes botanicae. Casterman-Dien, Tournay
• GISEKE, P.D. 1792. Praelectiones in ordines naturales plantarum. B.G. Hoffmann, Hamburg
• HARVEY, W.H. 1865. Compositae. Flora capensis 3
• HILLIARD, O.M. 1977. Compositae in Natal. University of Natal Press, Pietermaritzburg
• JEFFREY, C. & POPE, G.V. 1992. Compositae. Flora zambesiaca 6,1
• KARIS, P.O. 1992. Hoplophyllum DC., the sister group to Eremothamnus O.Hoffm. (Asteraceae). Taxon 41
• KEELEY, S.C. & JANSEN, R.K. 1991. Evidence from chloroplast DNA for the recognition of a new tribe, the Tarchonantheae, and the tribal placement of Pluchea (Asteraceae). Systematic Botany 16
• MERXMÜLLER, H. 1967a. Asteraceae. Prodromus einer Flora von Südwestafrika 139
• MERXMÜLLER, H. 1967b. Cichoriaceae. Prodromus einer Flora von Südwestafrika 140
• POPE, G.V. 1992. 97. Compositae. Flora zambesiaca 6,1
• ROBINSON, H. 1992. Observations on the unique form of sweeping hairs on the styles of the Eremothamneae (Asteraceae). Taxon 41

Resources:

• Classification of Asteraceae
• Key to Asteraceae tribes
• Key to Asteraceae genera (Intermediate ranks omitted)

• Asteraceae Tribes:

• Asteraceae genera: