Taraxacum lactucifolium Kirschner & Štěpánek, 2023

Kirschner, Jan & Štěpánek, Jan, 2023, A taxonomic revision of Taraxacum sect. Dissecta, a continental steppe group common in Siberia and adjacent regions of Central Asia, Phytotaxa 590 (1), pp. 1921-1935 : 1921-1935

2. Taraxacum lactucifolium Kirschner & Štěpánek , sp. nov.

Type:—[ RUSSIA, Irkutskaya oblast] Sibiria merid., urbs Irkutsk, lacus Bajkal, pagus Listvjanka , in decl. stepposis supra portum in pago Listvjanka [City of Irkutsk, Baikal Lake, village of Listvyanka, steppe slopes above the port in the village, ca. 51° 51’ N, 104° 52’ E, ca. 500 m a.s.l.], 26 Oct 1985, J. Kirschner & J. Štěpánek 1575/30, cultivated as JŠ 2713 ( PRA, no. det. 35844, holotype; isotype: PRA, no. det. 36681)

Etymology:—Leaf shape similar to Lactuca .

Exsiccates:— Taraxaca Exs., no. 1380.

Diagnosis:—Plantae notabiles foliis profunde pinnatisectis, segmentis lateralibus et interlobiis conspicue lobulatis et dentatis, phyllariis involucralibus exterioribus adpressis, lanceolatis, aequaliter olivaceo-viridibus, marginibus saepissime indistinctis membranaceis vel scariosis plerumque 0.1–0.2 mm latis, acheniis brunneis vel pallide brunneis brevibus, corpore dense breviter spinuloso, in pyramidem subcylindricam 0.5–0.7 mm longam abrupte transeunte.

Plants small, usually to 12 cm tall. Petiole short, unwinged to narrowly winged, sparsely arachnoid, usually suffused purplish; plant base with yellowish hairs, tunic developed. Leaves ± deep green, sparsely arachnoid, later glabrescent, usually narrowly elliptical in outline, 6–12 × 1.5–2.8 cm, with a complicated leaf shape pattern, deeply pinnatisect, usually with 5–7 pairs of patent, subhamate or subrecurved, usually linear-triangular lateral segments, frequently with broad base abruptly narrowed in the linear to linear-lingulate distal part, distal margin convex or subconcave, seldom entire, usually with a few little teeth and with 1–2 lobules near segment’s base, proximal margin most often concave, entire; terminal segment tripartite, with distal lobe linear-lingulate to narrowly triangular, often dilated at base, entire or more often with a pair of patent lobules, basal lobules linear, patent, entire; interlobes narrow, usually 1–2 mm wide, usually irregularly dentate and lobulate, some lobules with shape and size similar to that of lateral segments; midvein glabrous to sparsely arachnoid, often suffused brownish-purplish. Scapes green or suffused purplish, arachnoid, subequalling leaves. Capitulum yellow, 3–3.5 cm wide. Involucre olivaceous-green to dark olivaceous, 8–10 mm wide and rounded at base. Outer phyllaries 10–13, ± appressed, sometimes loosely so, not imbricate, lanceolate, usually 5–7.5 (–8) × 2.2–3.5 mm, ± evenly coloured olivaceous-green, darker distally, border usually not very distinct, membranous or whitish-membranous, 0.1–0.2 (–0.4) mm wide, sometimes with paler yellowish-green border zone to 1 mm wide in basal part of some phyllaries, all colour transitions on phyllary surface gradual, margin ciliate, apex flat to callose; inner phyllaries 11–13 mm long, flat. Outer ligules flat, striped light grey-purplish outside, inner ligule teeth dirty yellow or greyish. Stigmas light yellow-green, with pubescence of mixed hyaline and grey hairs. Pollen present, pollen grains irregular in size. Achenes light medium-brown to medium-brown, 3.1–3.6 × 0.8–0.9 mm, body shortly, ± densely spinulose in upper 1/3, ± abruptly narrowing into subcylindrical cone 0.5–0.7 mm long; beak 9–10 mm long, pappus 5–5.5 mm long, yellowish white. – Agamosperm. – Fig. 3 .

Diagnostic notes:—The combination of pure brown achenes and lanceolate, usually very narrowly bordered outer phyllaries, with a complicated leaf shape pattern of numerous narrow, lobulate and/or dentate lateral segments and interlobes is diagnostic.

Distribution and habitat:— Taraxacum lactucifolium was primarily sampled at steppe patches on slopes above Lake Baikal, in the vicinity of Listvyanka village, at about 500 m. There is another, very remote locality, near the mouth of Ob River in northern Siberia.

Specimens examined:—[ RUSSIA, Irkutskaya oblast] City of Irkutsk, Baikal Lake, village of Listvyanka , steppe slopes above the port in the village [ca. 51° 51’ N, 104° 52’ E, ca. 500 m a.s.l.], 26 Oct 1985, J. Kirschner & J. Štěpánek 1575/30, cultivated as JŠ 2713 ( PRA, no. det. 36681). – Northern Siberia , region of the mouth of Ob River [Yamalo- Nenets Autonomous Okrug, ca. 66° 39’ N, 66° 23’ E], in the village of Labytnangi, Aug 1987, L. Klimeš, cultivated as JŠ 3166 ( PRA, no. det. 35849) .

Figures

FIGURE 3. Taraxacum lactucifolium. A, General habit; B, Achenes (both from PRA, no. det. 35844, holotype).