Taraxacum leucocarpum Jurtzev & Tzvelev

Kirschner, Jan, Štěpánek, Jan & Buryy, Vladimir V., 2025, Towards a revision of Taraxacum sect. Borealia (Compositae, Crepidinae) in Siberia and the continental Far East, with special reference to the dandelions of the Altai and Kamchatka, Phytotaxa 679 (1), pp. 1-147 : 77-78

30. Taraxacum leucocarpum Jurtzev & Tzvelev in Tzvelev & Jurtzev (1984: 188)

Type:—[ RUSSIA, Chukotka] Zapadnaya Chukotka, ostrov Ayon, k s-v ot posyolka, pravoberezh’ye r. Roveem , na razvevaemykh peskakh [ W. Chukotka, Ayon Island, NE. of the settlement, right banks of Roveem River, wind-blown sands], 13 Aug 1968, I. G. Levichev , A. A. Korobkov & B. A. Yurtzev s. n. ( LE, no. det. 17893, holotype; isotypes: 17152, 17153, 17154). – Possible isotype, with a slightly different locality wording: “elevated sandy floodplain of Reema R.”, 13 Aug 1968, I. G. Levichev, A. A. Korobkov & B. A. Yurtzev s. n. ( LE, no. det. 6078, with a note “2n = 16”) .

Etymology:—With white (or whitish) fruits.

Plants ± slender, 8–12 cm tall. Petiole pale, often suffused purplish, ± glabrous, narrow, unwinged; plant base without tunic, with sparse arachnoid hairs among petioles. Leaves light mid-green, glabrous or subglabrous, linear to linear-oblong, ca. 4–9 × 0.5–1.4 cm, rarely undivided and remotely lobulate, usually irregularly pinnatisect, with 2–4 pairs of lateral segments, usually patent or hamate-recurved, acute to acuminate, triangular to linear-triangular, distal margin usually convex, with unequal teeth and narrow lobules (often descending to the interlobe), proximal margin straight to concave, usually ± entire; terminal segment, narrow, elongated, linear-triangular, with irregular teeth and lobules, mainly near its base; interlobes very narrow or medium broad, usually with irregular teeth and lobules; mid-vein pale green or purple. Scapes brownish green, glabrous or with scattered arachnoid hairs distally, usually shorter than leaves. Capitulum light yellow, ± small, 1.5–2.5 cm wide. Involucre black-green, not pruinose, 7–8 mm wide and narrowly rounded at base. Outer phyllaries ca. 8–11, appressed, ± not imbricate, ovate-lanceolate to lanceolate, usually 5–7 (–8) × 1.8–2.5 mm, surface ± evenly black-green (black when dry), rarely dark olivaceous-green, border ± absent, or indistinct, very narrow, less than 0.1 mm wide (better visible in olivaceous-green phyllaries), margin ± glabrous, apex usually corniculate, sometimes with well developed horns, rarely ± flat; inner phyllaries blackish olivaceous-green, often coalescing, 11–13 mm long, corniculate. Outer ligules flat, variably, usually faintly striped light pinkish grey outside, ligule teeth dirty yellow. Stigmas discoloured, ± greenish. Pollen present, pollen grains of regular size. Achenes light greyish or whitish grey (with occasional, not rare, occurrence of sterile, ± white, thin achenes), 5.2–5.6 × 1.0– 1.2 mm, body sparsely shortly spinulose in upper 1/5–1/4, spinules erect to curved upwards, short, up to 0.2 mm long, ± robust, mostly confined to longitudinal ridges, body gradually narrowing in a conical cone (0.5–) 0.7–0.8 (–0.9) mm long, ca. 0.5–0.6 mm thick at base, 0.3–0.35 mm distally; beak usually 3–4 mm long; pappus yellowish, ca. 6.5 mm long. – 2n=16 (counted by P. G. Zhukova, under no. SG-68-41). – Sexual. – Fig. 49 , 50 .

Diagnostic notes:—The intermediate position between T. sect. Arctica and T. sect. Borealia and the sexual reproduction make T. leucocarpum an exceptional taxon. When compared with members of the latter section, it may be considered close to T. lenense , T. lateritium , T. macilentum and T. kolymense . The sparsely shortly spinulose achenes with a conical cone, few outer phyllaries and the peculiar leaf shape are diagnostic.

Distribution and habitat:— Taraxacum leucocarpum is known from a single macrolocality in Ayon Island, the NW. Chukotka. The habitat is sandy, on a river terrace.

Species with outer phyllaries linear-lanceolate to lanceolate, usually erect-patent to patent, or arcuate-patent

This peculiar group is confined to the Altai, according to the material available. The conspicuously horned but not appressed outer phyllaries and the conspicuous heterophyly characterize both species included in it.

Figures

FIGURE 49. Taraxacum leucocarpum. A, general habit (a plant of the holotype herbarium sheet, LE, no. det. 17893); B, achenes (LE, no. det. 6078). Scale bars: A = 2 cm; B = 1 mm.

FIGURE 50. Taraxacum leucocarpum. General habit (LE, no. det. 17153).