Two new species from Mexico are described, Simsia sylvicola from Oaxaca and S. spooneri from Guerrero. The two species are placed in Simsia because they exhibit most of the features that characterize the genus, although they differ in possessing a biconvex achene shape that is more typical of the related genus Viguiera. Chromosome counts of n = 17 are reported for both species. In the course of our revisionary studies of Viguiera Kunth ser. Grammatoglossae S. F. Blake, we have discovered two previously undescribed species. There is some question whether these should be placed in Viguiera or in the related Simsia Persoon, because the distinction between these genera is still problematic. In practice, Spooner (1990) considered Simsia to be delimited by features of the disk achenes, which are laterally very flattened and usually have a pappus of two awns but typically lack squamellae. In contrast, the typical disk achene in Viguiera is biconvex and has a pappus that includes both two awns and also two or more squamellae. There is, however, a larger suite of traits that, together with the achene features, characterize Simsia (Spooner, 1990), including nodal disks, herbaceous involucres, long, narrow ray ovaries, long, tapering style branches, and setose anther connectives. Many of these traits are also exhibited in combination by some of the members of Viguiera ser. Grammatoglossae. The two new species are particularly striking in differing from typical members of Simsia only in features of the achene, and thus further bridge the morphological distinction between the two groups. Further support indicating that Simsia and some members of Viguiera ser. Grammatoglossae are related phylogenetically has been revealed from restriction site analysis of chloroplast DNA (Schilling & Jansen, 1989; Schilling & Panero, unpublished data). Resolution of the exact boundaries between Simsia and Viguiera ser. Grammatoglossae will await further information from DNA-based studies. We argue at this point that the concept of Simsia should be broadened relative to that of Spooner (1990) to include some species that have biconvex achenes (there is, in fact, variation within one species of Simsia, S. ghiesbreghtii (A. Gray) S. F. Blake, for this trait). For this reason, we suggest placement in Simsia of the two species newly described here, S. sylvicola and S. spooneri. Simsia sylvicola Panero & E. Schilling, sp. nov. TYPE: Mexico. Oaxaca: Km 65 of the road Oaxaca-Sola de Vega, occasional in pine-oak forest, 1,950 m, 10 Nov. 1990, Panero 2106 (holotype, MEXU; isotypes, ENCB, SI, TENN, TEX, US). Figure 1. A Viguiera rhombifolia (Robinson & Greenman) S. F. Blake foliis perfoliatis et late deltatis et petiolis plerumque non alatis differt. Perennial herbs 4-10 dm tall, sometimes prostrate. Stems terete, purplish brown, sparsely to moderately puberulent, hispid distally toward the capitulescence. Leaves opposite, triplinerved; petioles 10-23 mm long, terete to slightly canaliculate, sparsely to moderately puberulent to hispid; blades 4-7 cm long, 12-55 mm wide, gradually decreasing in size distally toward the capitulescence, deltate to ovate, base rounded to truncate, apex acuminate, margins serrate to dentate, adaxial surface shiny dark green drying dull brownish green, sparsely to moderately strigose to hirsute, abaxial surface slightly paler in color than adaxial surface, moderately hirsute, pubescence denser on veins outlining them against a green background. Capitulescences dichasial, thyrsoid, open or sometimes heads congested at distal end of peduncles with 3-25+ heads; peduncles 2-30 cm long, pubescence like that of the stem. Heads 6.5-7.5 mm diam. (ligules excluded), 12-13 mm high, campanulate to cylindrical; receptacles 4.5-5.5 mm diam. in fruit, flat to slightly convex. Phyllaries 19-23 in 3 graduated series; phyllaries of first series 3-5.5 mm long, 1.2-1.5 mm wide, ovate to lanceolate, herbaceous, dark NOVON 2: 385-388. 1992. This content downloaded from 157.55.39.35 on Mon, 29 Aug 2016 06:13:12 UTC All use subject to http://about.jstor.org/terms