Flora del Cono Sur · Ficha del taxón
Annual herbs, ca. 35 cm tall, stem solitary, erect, branched from near base to upper part, uniformly and loosely leafy, glandular-lanuginose. Leaves 50–70 × 7–9 mm, obovate, long-attenuate at base, apex acute, mucronate; discolorous, greenish glandular on upper surface, whitish-woolly on lower surface; trichomes long, eglandular, eseptate, with basal cells expanded. Capit ula many, in headlike clusters, on terminal branchlets, subtended by linear leaves, forming leafy, paniculate synflorescence. Involucre campanulate, 4–4.5 × 3–4 mm. Phyllaries ca. 19, 3-seriate, lamina light brown at apex; outer phyllaries ca. 3 × 1 mm, ovate, apex acum inate, lanuginose; inner phyllaries ca. 4 × 0.7 mm, lan ceolate, apex acute, glabrous. Pistillate florets ca. 83, corolla ca. 2.5 mm. Bisexual florets ca. 4, corolla ca. 2.5 mm, 5-lobed, anthers 5. Achenes ca. 0.6 mm, pilose, with short, globose duplex trichomes. Pappus bristles ca. 2.5 mm.
Brazil. Rio de Janeiro: Guanabara, Gávea, 10 Mar. 1946, C. T. Rizzini 82 (holotype, LP-000233!*).
Gamochaeta rizzinii is endemic to southern and southeastern Brazil (Cabrera, 1961; Flora e Funga do Brasil, 2023) in the Amazonian and Chacoan dominions (Cabrera & Willink, 1973), where it grows on rocky outcrops at the edge of the Atlantic Forest (Deble & Marchiori, 2007).
Sin datos de conservación registrados en Flora Vascular Argentina.
Fuente: Flora Vascular Argentina.
Recognition. The cluster analysis (Fig. 3A) shows that Gamochaeta rizzinii is grouped with G. grazielae. Both species have stems branched near the base and discolorous leaves. However, G. rizzinii differs by its capitula in headlike clusters arranged in leafy, panic ulate synflorescences (vs. capitula in continuous spikes interrupted at base) and adaxial leaf surfaces glandu lose (vs. sparsely arachnoid or lanuginose).