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(Last Modified On 6/6/2013)
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(Last Modified On 6/6/2013)
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Genus
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Stevia Cav.
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PlaceOfPublication
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Icon. Descr. P1. 4: 32. 1797.
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Note
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TYPE: S. serrata Cav. (see King & Robinson, 1969).
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Synonym
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Mustelia Spreng., Nacht. 1, Bot. Gart. Halle 28. 1801. TYPE: M. eupatoria Spreng. Nothites Cass., Dict. Sci. Nat. 35: 163. 1825. TYPE: N. latifolia Cass. = Stevia melissaefolia (Lam.) Schultz-Bip. Xetoligus Raf., New Fl. Bot. N. Amer. 4: 74. 1836. TYPE: Stevia salicifolia Cav.
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Description
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Mostly erect annual or perennial herbs or shrubs, sparingly to densely branched. Leaves opposite or alternate, sessile to distinctly petiolate; blades linear to orbicular, the margins entire to serrate or dentate, rarely deeply lobed, the surface usually puberulous or stipitate-glandular, usually glandular punctate. Inflorescence diffuse with few long-pedunculate heads or dense in corymbose panicles. Heads discoid with 5 florets; involucre narrowly cylindrical; involucral bracts 5, eximbricate, in 1 series, linear to elliptical, easily torn from receptacle; receptacle glabrous; corolla narrowly funnelform or with somewhat expanded throat, usually with hairs or glands on outer surface and with hairs on inner surface, the cells of the limb elongate with sinuous walls, the lobes rarely to 2 mm long, shorter than throat and tube, oblong-ovate, sometimes zygomorphic with outer lobes longer, densely papillose oui inner surface, smooth on outer surface; anther collars cylindrical to larger below, with many quadrate to short-oblong cells below, the cel-l walls with variably annulate thickenings, the exothecial cells subquadrate to short-oblong, the anther appendage mostly obovate with prominently crenulate distal margin; style base with distinct enlargement, glabrous, or in a few species papillose, the style appendages filiform, densely
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Habit
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herbs or shrubs
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Description
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long-papillose. Achenes fusiform to cylindrical, strongly 5-ribbed with few to many glands or bristles; carpopodium distinct, short, slightly asymmetric with a few rows of small quadrate to short-oblong cells; pappus with at least a crown of free to united scales, often with 1-30 awns or bristles; one of the achenes in each head often with more reduced pappus. Pollen with short spines, sometimes with complex furrows or cylindrical to dumbbell shaped.
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Distribution
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The genus Stevia contains about 150-200 species (Grashoff, 1972) and ranges from the southwestern United States through Mexico, Central America, and South America to Argentina. Four species have been collected in Panama.
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Reference
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Grashoff, J. L. 1972. A systematic study of the North and Central American species of Stevia. Ph.D. dissertation, University of Texas. 608 pp. Microfilm 73-7556. King, R. M. & H. Robinson. 1967. Multiple pollen forms in two species of the genus, Stevia (Compositae). Sida 3: 165-169. King & Robinson. 1968. Studies in the Compositae-Eupatorieae. VIII. Observa- tions on the microstructure of Stevia. Sida 3: 257-269. Robinson, B. L. 1930a. Observations on the genus Stevia. Contr. Gray Herb. 90: 36-58. Robinson, B.L. 1930b. The Stevias of North America. Contr. Gray Herb. 90: 90-160.
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Key
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a. Shrub; leaves glabrous, the veins pinnate; corolla lobes glabrous on outer surface ...... 2. S. lucida aa. Perennial herbs or subshrubs; leaves puberulous at least on veins, the veins weakly to strongly trinervate; corolla lobes with few to many hairs oil outer surface. b. Pedicels and involucral bracts with few to many stipitate glandular hairs ...... 1. S. caracasana bb. Pedicels and involucral bracts with only nonglandular hairs and glandular punctations. c. Leaves puberulous to subtomentose on lower surface; involucral bracts long-acute or slightly acuminate, scarcely scarious at tips; achenes without pappus awns ...... 4. S. triflora cc. Leaves puberulous only on veins of lower surface; involucral bracts usually short- acute, often broadly scarious at tips; usually some achenes with 1-2 pappus awns ...... 3. S. ovata
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