Helianthus dentatus Cavanilles 1794

Helianthus dentatus Cavanilles (1794: 10)

Type:—'Habitat in Imperio Mexicano cum praecedente. Florebat in Regio horto Matritense mensibus Octobri et Novembri' [Helianthus linearis Cavanilles —'Habitat in imperio Mexicano, prope oppidum Hapam'], A. J. Cavanilles s.n. (lectotype: MA 475778 [scan seen], designated here).Ξ Viguiera dentata (Cav.) Sprengel. Fig. 1.

Of the four sheets of H. dentatus in the Cavanilles herbarium, only the sheet MA 475778 has label information annotated by Cavanilles (Garilleti 1993) and with an indication that the plant was cultivated in the Real Jardín Botánico (Fig. 1). The plate number from the Icones (T. 220) also appears on the label. The plate of Cavanilles does not exactly match with none of the four sheets of H. dentatus in the Cavanilles herbarium. But careful observations of the biggest fragment on the sheet MA 475778 allow to observe a great similarity between the plant's drawing (T. 220) and the exsicata fragment (which is in an inverted position, in relation to the plant's drawing). The label on the sheet MA 475779 was not written by Cavanilles but by J. D. Rodríguez (Blanco et al. 2010) and is dated 1801 (after the publication of the Icones). The two remaining sheets have the same number, MA 475777, one of them with two handwritten labels, but neither in Cavanilles' hand.

Viguiera dentata shows remarkable phenotypic plasticity and considerable resistance to drought and heat (Sarquis et al. 2010). It occurs in dry areas (slopes, canyons, fields, and roadside ditches) in the southwestern United States, Mexico, West Indies (Cuba) and Central America (Schilling 2006). More studies are necessary to determine if the four varieties currently accepted for V. dentata should be elevated to the species level (Blake 1918, Schilling & Panero 2011). This emphasizes the importance of selecting a type for V. dentata.