Plazia Ruiz & Pav., Fl. Peruv. Prodr.: 92. 1794.

Dillon, Michael O. & Luebert, Federico, 2014, Synopsis of Plazia Ruiz & Pav. (Onoserideae, Asteraceae), including a new species from northern Peru, PhytoKeys 34, pp. 1-13 : 1-2

Plazia Ruiz & Pav., Fl. Peruv. Prodr.: 92. 1794.

Aglaodendron J. Rémy, Ann. Sci. Nat., ser. 3, 12: 175. 1849. Type: Aglaodendron cheiranthifolium J. Rémy = Plazia cheiranthifolia (J. Rémy) Wedd.

Harthamnus H.Rob., Phytologia 45(6): 451. 1980. Type: Harthamnus boliviensis H. Rob. = Plazia daphnoides Wedd.

Type.

Plazia conferta Ruiz & Pav.

Description.

Shrubs 1-2 m tall, the branches erect to ascending; stems lacking spines. Leaves simple, sessile, in whorls at branch tips; blades lanceolate to oblanceolate, glabrous to glandular, usually appressed, the margins entire. Capitulescences of solitary, terminal heads, sessile. Capitula heterogamous, radiate or more rarely homogamous, discoid; involucres cylindrical to campanulate; receptacles plane, glabrous; phyllaries 5-7-seriate, lanceolate; ray florets 5-25, the corollas ligulate-bilabiate, the outer lip 4-nerved, tridentate, the inner lip bifid; styles cylindric, glabrous, bifid, the branches short, inconspicuous; disc florets 7-40, the corollas tubular, actinomorphic, glabrous, the limb deeply 5 -lobed, the lobes greater than 1/3 the length of the corolla, coiled; anthers linear, the terminal appendages lanceolate, fused into a column, truncate, the bases caudate; styles claviform, the branches short, rounded. Achenes glabrous or glandular-pubescent; pappus of scabrid bristles, isomorphic, yellowish. Chromosome number: unknown.

Distribution.

All species are confined to the Andean Cordillera and associated inter-Andean valleys ( Fig. 1 ). Two species are confinded to Peru; both are rare and only known from a few collection localities. Another species is restricted to the Andes of central Chile. Plazia daphanoides Wedd. is the only wideranging species, being recorded from southern Peru and adjacent Argentina, Bolivia and Chile, usually in high-elevation, dry sites ( Cabrera 1978, Ferreyra 1980, 1995).

Discussion.

The genus Plazia was described by Ruiz López and Pavón (1794) and they subsequently published its first species, Plazia conferta Ruiz & Pav. (1798). All efforts at locating material corresponding to their type collection from Peru have not been successful ( Cabrera 1960).

Weddell (1855) provided an emended generic description for Plazia and he recognized three species: Plazia conferta Ruiz & Pav., Plazia cheiranthifolia (J. Remy) Wedd., and Plazia daphnoides Wedd. Reiche (1905) picked up the implied transfers by Hoffmann (1890-1894) and treated Plazia in Chile as having three species: Plazia cheiranthifolia , Plazia pinifolia (Phil.) O.Hoffm. [= Gypothamnium pinifolium Phil.], and Plazia virgata (Phil.) O.Hoffmann [= Aphyllocladus denticulatus (J. Rémy ex Gay) Cabrera]. Recent floristic treatments have accepted Plazia as distinct from Aphyllocladus and Gypothamnium (e.g., Cabrera 1978, Ferreyra 1995, Hind 2009, Marticorena and Quezada 1985, Zuloaga and Morrone 1999). The addition of the northern Peruvian species described here brings the total number of recognized species to four.

Key to species of Plazia

1	Leaves oblong or oblong-spathulate, 8-18 mm long, 2-3.5 mm wide; capitula with 5-8(-10) ray florets, (7-)10-11(-12) disc florets; involucres cylindrical (Argentina, Bolivia, Chile, Peru)	Plazia daphnoides Wedd.
-	Leaves elliptic to oblanceolate or oblong, 22-42 mm long, 3-6 mm wide; capitula lacking obvious ray florets or more commonly with 15-25 ray florets, (9-)20-25(-40) disc florets; involucres campanulate 2
2	Leaves oblong, 28-30 mm long, 7.5-8 mm; corollas more or less isomorphic, obvious ligules lacking (Central Chile)	Plazia cheiranthifolia (J. Rémy) Wedd.
-	Leaves oblanceolate, 10-25 mm long, 1-3 mm wide; corollas dimorphic, outer florets with ligules obvious (Peru)	3
3	Involucre 25-30 mm in diameter; ray florets 15-20, disc florets c. 40	Plazia robinsonii M.O.Dillon & Sagást.
-	Involucre 12-16 mm in diameter; ray florets18-20, disc florets 10-20	Plazia conferta Ruiz & Pav.

Figures

Figure 1. Distribution map of the currently recognized species of Plazia. The shaded area indicates high-elevation areas of the Andes above 3000 m. Locality data were obtained from Cabrera (1951), Ferreyra (1995), Missouri Botanical Garden (http: // www. tropicos. org /), Instituto de Botanica Darwinion (through http: // www. gbif. org /) and the herbaria ASU, B, F, HUT, P, SGO, US.