Tonestus eximius (H. M. Hall) A. Nels. & J. F. Macbr.

Tonestus eximius is known only from the upper elevations of the Sierra Nevada in the vicinity of Lake Tahoe in Alpine and El Dorado counties, California, and Washoe County, Nevada. It is similar to Lorandersonia peirsonii, although smaller in most respects.

Perennials, cespitose, 5–13 cm ; with branched caudices surmounting ± well-developed taproots, or short rhizomes. Stems (clothed with marcescent leaf bases) glabrous, densely stipitate-glandular. Leaves: basal blades broadly spatulate, 20–35 × 12–15 mm, margins coarsely, irregularly serrate to dentate; cauline blades oblong, 9–52 × 5–15 mm, ± reduced distally, margins coarsely, irregularly serrate or nearly entire; 1- or 3-nerved, margins stipitate-glandular, faces glabrous, stipitate-glandular. Heads usually borne singly, sometimes 2–4. Peduncles 2 –15 mm. Involucres broadly campanulate, 9–16(–20) × 5–11(–15) mm. Phyllaries 16–32 in 3–4 series, 1- or weakly 3-nerved, ± equal, margins eciliate; outer and mid green, oblong, 6–10 × 2–5 mm, foliaceous, apices rounded or obtuse to acute; inner green or sometimes anthocyanic, linear, 7–9 × 0.5–2 mm, chartaceous proximally, margins scarious, fimbriate and/or stipitate-glandular distally, apices acute to acuminate, often reflexed, faces stipitate-glandular distally. Ray florets 10–13; laminae elliptic, 5–8 × 1–3 mm. Disc florets 41–49; corollas narrowly funnelform, 5.5–7.5(–8.2) mm, exceeding involucres, lobes erect, 0.7–1.7 mm, ¹ / 10 – ¹ / 5 corolla length; anthers 2.5–3.3 mm; style-branch appendages subulate, 0.9–1.3 mm, stigmatic lines 0.9–1.6 mm. Cypselae linear, 2.5–6 mm, 5–9-nerved, faces villous, often ± viscid; pappus bristles 19–43, brittle. 2n = 18.

Haplopappus eximius H. M. Hall, Univ. Calif. Publ. Bot. 6: 170, fig. 2, plate 20. 1915

Tonestus eximius is a species of flowering plant in the family Asteraceae known by the common names Lake Tahoe serpentweed and Tahoe tonestus. It is native to the High Sierra Nevada, where it is known only from the vicinity of Lake Tahoe on the California-Nevada border. It grows in alpine and subalpine mountain habitat. It is a short, clumpy perennial herb growing up to 13 centimeters tall. The thick stems are hairless and glandular, the lower parts covered in the withered leaf bases of previous seasons' growth. The toothed or serrated leaf blades are up to 3 to 5 centimeters in length. The inflorescence is a single flower head or a cluster of a few heads. Each is 1 to 1.5 centimeters wide with green phyllaries. The head bears at least 10 bright yellow ray florets around a center containing many tubular disc florets.

Tonestus eximius là một loài thực vật có hoa trong họ Cúc. Loài này được (H.M.Hall) A.Nelson & J.F.Macbr. miêu tả khoa học đầu tiên năm 1918.