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Project Name Data (Last Modified On 6/20/2013)
 

Flora Data (Last Modified On 6/20/2013)
Genus Senecio L.
PlaceOfPublication Sp. P1. 866. 1753
Note TYPE: S. vulgaris L
Description Herbs, shrubs, small trees or lianas. Leaves alternate, simple, pinnately veined, or in 1 species, palmately veined. Inflorescence a few-many-headed corymbiform cyme arising terminally or in the axils of the upper leaves, or occasionally heads solitary. Heads radiate or discoid, rarely disciform, red to orange-red or yellow, sometimes ochroleucous; principal involucral bracts of equal length in a single series or obscurely divisible into an inner and outer series, usually subtended by a calyculus of 10 or fewer irregular bractlets; receptacle flat to gently convex, naked, sometimes obscurely alveolate or with minute hairlike paleas irregularly disposed among the achenes, conspicuous paleas lacking; ray florets fertile, in a single series, the ligule usually well developed but sometimes reduced and inconspicuous, ray florets sometimes absent; disc florets fertile, bisexual, the style branches variously tipped with a penicilliate tuft of hairs to a distinct, triangular appendage. Achene terete or ribbed, glabrous or variously pubescent; pappus of a single series of white, capillary bristles.
Habit Herbs, shrubs, small trees or lianas
Distribution A huge complex of more than 1500 species in both the Old and New Worlds
Note Senecio is readily divisible into semidistinct groups. Some contemporary botanists advocate the recognition of several segregate genera, but the broad traditional concept of Senecio has been maintained in this treatment.
Reference Beaman, J. H., D. C. D. Dejong & W. P. Stoutamire. 1962. Chromosome studies in the alpine and subalpine floras of Mexico and Guatemala. Amer. Jour. Bot. 49: 41-50. Cabrera, A. L. 1950. Notes on the Brazilian Senecioneae. Brittonia 7: 53-74. Cuatrecasas, J. 1955. A new genus and other novelties in Compositae. Brittonia 8: 151-153. Greenman, J. M. 1901. Monographie der nord-und centralamerikanischen Arten der Gattung Senecio. 1 Teil. Leipzig. 37 pp. [Reprinted in Bot. Jahrb. Syst. 32: 1-33. 1902.] Robinson, H. & R. D. Brettell. 1973. Studies in the Senecioneae (Asteraceae) V. The genera Psacaliopsis, Barkleyanthus, Telanthophora and Roldana. Phytologia 27: 402-439. Williams, L. 0. 1975. Tropical American plants, XVIII. Phytologia 31: 435-447.
Key a. Erect herbs, shrubs or small trees, not scrambling lianas. b. Cauline leaves palmately veined ...... 6. S. heterogamus bb. Cauline leaves pinnately veined. c. Leaves densely white lanate-tomentose throughout, at most glabrate on the upper leaf-surfaces ...... 8. S. oerstedianus cc. Leaves variously pubescent to glabrous but not densely white-lanate-tomentose. d. Leaves large, blades 15-35 cm long, deeply sinuate with 3-6 conspicuous sinuses on each side of the leaf ...... 2. S. arborescens dd. Leaves normally smaller, dentate to entire but not both large and deeply sinuate. e. Involucral bracts 13-17(-18), the calyculate (basal) bracts 6 or more, conspicuous, often more than 5 mm long, the involucre often purplish ...... 3 . S . b o q u e te n sis ee. Involucral bracts ca. 8, the calyculate (basal) bracts 4 or fewer, rarely more than 4 mm long. f. Heads narrowly cylindrical; involucral bracts linear-oblong, more than 8 mm long; ligules ca. 10 mm long in dried specimens ...... 5. S. cooperi ff. Heads broader upwards, at least at maturity; involucral bracts lanceolate-spatulate, 6-7 mm long; ligules 5-8 mm long ...... 7. S. megaphyllus aa. Lianas. g. Heads large, campanulate; principal involucral bracts 30-40'; ray florets 18-24, the style branches surmounted by distinctly expanded, papillose, triangular tips ...... 4. S. confusus gg. Heads smaller; principal involucral bracts 10 or fewer; style branches surmounted by penicilliate hairs. h. Heads radiate, -the ligules long and narrow, ca. 10-15 mm long, less than 1 mm wide; leaves, especially the lower surfaces, with stipitate-stellate hairs ...... 1. S. angustiradiatus hh. Heads disciform or with ligules less than 1 mm long; leaves glabrescent, sometimes with scattered simple hairs ...... 9. S. parasiticus
 
 
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