Scrambling shrubs, moderately branching, stems terete to strongly hexagonal, mostly tomentose, without latex; nodes with or without disks; leaves opposite; petioles with or without wings, sometimes included in perfoliate leaf pairs; blades sharply delimited and rounded to slightly cordate at base or confluent with petiole, ovate to oblong-ovate, margins subentire to serrate, never angulate, upper surface flat to slightly bullate, densely tomentose below, pinnately veined. Inflorescence terminal on branches, corymbiform, peduncles less than 5 cm long, thinly to densely tomentose. Heads with involucres broadly campanulate, involucral bracts 30-55 in 4-5 series, narrowly ovate to lanceolate. tips obtuse to narrowly acute, outer surface puberulous to arachnoid tomentose or hirsute. Ray florets 6-18, female; corollas yellow, with elliptical limbs; style branches not spiraled. Disk florets 10-34, bisexual; corollas yellow, narrowly funnelform, lobes 5, linear lanceolate, slightly longer than throat, without evident stomata; anther filaments smooth, with weak annular thickenings in walls; thecae pale, digitate at base; endothecial cells oblong, with oval or strap-shaped sclerified bands, with single thickening on each transverse wall; apical appendages oblong-ovate, smooth with short-oblong to subquadrate cells. Nectary short, not or scarcely lobed. Style base scarcely broadened; style branches up to 20 times as long as wide, ca. 1.5 times as long as hispidulous part of upper style shaft, tips narrowly obtuse. Achenes prismatic, with 5-8 ribs, bearing contorted setulae and small glandular dots, cells of achene wall with subquadrate raphids; carpopodium short, annuliform, with small subquadrate cells in 3-5 series, walls of cells moderately thickened; pappus with 20-35 rather persistent inner capillary setae sometimes with broadened tips, with teeth of setae appearing mucronate-tipped in Hoyer's solution, with outer series of 7-20 short setae or squamellae. Pollen spherical, 30-37 µm in diam., with spines rather unevenly dispersed, with distinct group of inner columellae under each spine.
The genus Sampera is distributed from Colombia southward to northern Peru with the majority of the species in Ecuador. The genus Oligactis, as now limited, has species found in Costa Rica, Panama, Colombia and Venezuela. The new genus contains eight species.
Key to the species of Sampera
1a. Median involucral bracts ovate, shortly acute; longer pappus bristles thickened, especially at tips; upper surfaces of leaf blades smooth or with exsulcate venation . . . . . . . . . . 2
2a. Nodes with stipuliform disks to 3 or 4 times as wide as the stem; heads usually with 12 ray florets and 12 disk florets. . . . . S. ochracea
2b. Nodes without stipuliform disks or with disks not more than twice as wide as the stem; heads with 2-10 ray florets and ca. 10-15 disc florets. . . . . . . . . . . . . 3
3a. Heads with 2-4 ray florets and ca. 15 disk florets; lower surfaces of leaves with thin tomentum allowing dark color of secondary veins to show. . . . . . . . . S. cuatrecasasii
3b. Heads with 8-10 ray florets and ca. 10 disk florets; lower surfaces of leaves with thick tomentum obscuring color of secondary veins . . . . . . . . . . . S. coriacea
1b. All involucral bracts lanceolate, narrowly acute; longer pappus bristles slender with tips only slightly broadened; upper surfaces of leaf blades often rugose or bullate. . . . . . 4
4a. Leaf blades ovate-lanceolate; peduncles with appressed arachnoid tomentum; plants from near or below 2500 m . . . . S. asplundii