Taraxacum macroceras Dahlstedt (1906: 15)

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 : 30-31

6. Taraxacum macroceras Dahlstedt (1906: 15)

Type:—[ RUSSIA, Sakha Republic] Lena, Bulun , Jul 1898, N. H . Nilsson ( S, syntype, not located in S; cultivated, LD, no. det. 17835, pseudosyntype). – Bulkur, 26 Jun 1898, N. H . Nilsson ( S, syntype, not located in S). – Kiisiu [probably Küsür, Kyusyur, cf. Hämet-Ahti 1970], 3 Aug 1901, A. K . Cajander ( H, syntype, n. v., not located in H). – Tit-Ary et Tulach-Chaja, 11 Sep 1901, A. K . Cajander ( H, syntype, n. v., not located in H) .

Etymology:—With large horns.

Plants medium-sized, to ca. 16 cm tall. Petiole narrowly winged or ± unwinged, often pinkish, tunic absent. Leaves ± light green, subglabrous, narrowly oblanceolate in outline, usually 7–11 × 1–2.5 cm, later leaves almost undivided, with acute, short lobules, to ca. 14 × 2.5 cm, early middle leaves pinnatisect, with 3–4 pairs of ± long, deltoid-triangular, ± patent, sometimes patent-subrecurved lateral segments, distal margin straight, entire or with 1–3 teeth, proximal margin straight, entire; terminal segment rhombic-triangular to triangular, ± entire, with patent short basal lobules (in later leaves, terminal segment elongated-triangular); interlobes distinct, ca. 0.5–1.0 × 0.2–0.4 cm, usually ± dentate; midvein often suffused pinkish. Scapes brownish green, ± arachnoid, overtopping leaves. Capitulum yellow, ca. 4–5 cm wide. Involucre ± deep olivaceous-green, 8–9 mm wide and ± rounded at base. Outer phyllaries ca. 12–16, appressed to loosely appressed, ± not imbricate, ovate-lanceolate, some (inner) lanceolate, usually 6.0–7.5 (–8.0) × (2.5–) 3.2–3.5 mm, surface dark olivaceous-green to blackish green, with ± black middle line, slightly paler submarginal zone and with a very gradual, almost indistinct transition into a variably broad membranous border 0.3–0.8 mm wide, margin sparsely ciliate distally, apex with dark horns 1–2 mm long; inner phyllaries deep olivaceous-green, ca. 12–13 mm long, corniculate. Outer ligules striped, sometimes faintly, pale greyish pink outside, teeth dirty yellow. Stigmas yellow or slightly dirty yellow. Pollen present, pollen grains irregular in size. Achenes light greyish stramineous-brown, ca. 4.5 × 1.3–1.4 mm, body ± densely spinulose in upper 1/3, gradually narrowing in a short, conical cone ca. 0.5 mm long; beak thin, 9–10 mm long, pappus white, 6–7 mm long. – Agamospermous. – Fig. 13 .

Diagnostic notes:— Taraxacum macroceras is characterized by relatively numerous outer phyllaries with a border not very distinct but consistently present, membranous, 0.3–0.8 mm wide. Its achenes are thick (1.3–1.4 mm), a feature unknown in this group and rare in this section, and the cone is conical, short, ca. 0.5 mm long. Taraxacum lauriferorum is among its closest neighbours but the achenes are diagnostic (a short, ± conical cone in T. macroceras , a long, subcylindrical cone in T. lauriferorum ). The main difference between T. xanthellum and T. macroceras consists in the shape and length of cone: conical, ca. 0.5 mm long in the latter, and thin, cylidrical, at least 0.7 mm long in the former.

Distribution:—The majority of syntypes, either in S, or in H, were not located. All of them were collected in the region of the lower Lena River, Sakha Republic.

Specimens examined:— RUSSIA. Sakha Republic, Bulun District, lower stream of Olenek River (72°22’N), right bank near the mouth of Tas-Yuryakh River , 7 Aug 1960, B. A. Yurtzev ( LE, photo!) .

Figures

FIGURE 13. Taraxacum macroceras. A, flower heads, scale bar = 1 cm; B, a detail of early middle leaves (both LD, no. det. 17835).