Taraxacum dilutum Dahlstedt (1926b: 4)

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 : 136-137

60. Taraxacum dilutum Dahlstedt (1926b: 4) Type:—[ RUSSIA, Kamchatka] Kamtchatka, bassein r. Paratunka, sel. Nikolaevsk [Paratunka River basin, village of Nikolaevsk], 11 Jul

1908, V. Komarov ( S 12-27577 !, syntype [lower quality]). – Kamtchatka, Klutschi , 18 Jun 1921 , R. Malaise 3358 ( S 12-27574 !,

syntype; S 05-8203 !, syntype). Etymology:—Faintly coloured, weak.

Plants small, of robust appearance, to ca. 8 cm tall. Petiole winged, light green, often suffused pinkish, subglabrous, tunic absent. Leaves light green, glabrous above, sparsely arachnoid along mid-vein beneath, narrowly oblanceolate in outline, ca. 4–7 × 1.2–1.8 cm, pinnatilobed to pinnatifid, with 2–3 (4) pairs of patent to subrecurved, deltoid-triangular, usually entire lateral segments; terminal segment narrowly triangular, ± entire, with patent, acute basal lobules; interlobes broad, entire or some with a single little tooth; mid-vein usually pale green. Scapes light brownish green, distally arachnoid, usually subequalling leaves. Capitulum light or pale yellow, ca. 3 cm wide. Involucre light olivaceous-green, ca. 7 mm wide and narrowly rounded at base. Outer phyllaries ca. 10–13, ±loosely appressed, not imbricate, linear-lanceolate to narrowly lanceolate, usually (4.8–) 5.5–6.5 (–7.0) × 1.3–2.5 mm, surface light olivaceous-green, with a slightly darker middle zone and a very gradual, variably broad transition in an indistinct, paler olivaceous-green to membranous border 0.3–0.6 mm wide, margin ± glabrous, sometimes denticulate, apex usually with a distinct, elongated, purplish green horn usually 1.5–2.5 mm long; inner phyllaries 12–14 mm long, light olivaceous-green, sometimes coalescing, with shorter horns ca. 0.6–0.8 mm long. Outer ligules ± flat, initially subtubular, very faintly striped pinkish or greyish outside, teeth pale greyish-pinkish, inner ligule teeth light grey. Stigmas light greenish yellow or light green, rarely darker. Pollen absent. Achenes light greyish stramineous-brown, ca. 3.7–4.0 × 0.8–0.9 mm, body subsparsely but distinctly spinulose in upper 1/3, subabruptly narrowing in a subcylindrical cone ca. 0.8 mm long; beak 7.5–8.5 mm, pappus white, ca. 6 mm long. – Agamospermous. – Fig. 96 .

Diagnostic notes:—The low number of outer phyllaries, their size and shape (up to 6.5 mm long, linear-lanceolate to narrowly lanceolate), very light discoloured, almost yellow stigmas, and the absence of pollen are diagnostic. This species, however, remains rather unclear because of a rather unusual development of important characters.

Distribution:—According to the material available, T. dilutum is confined to Kamchatka (Klyuchi, Paratunka River and Esso). The new gathering from the vicinity of Esso is in good agreement with the type material (pollen absent, stigmas light to medium discoloured); the description of achenes is based upon the latter material.

Specimens examined:— RUSSIA. Bystrinskiy District , Bystrinskiy Nature Park , about 30 km from Esso towards Petropavlovsk-Kamchtskiy, 18 Jun 2014, V. V. Buryy (herb. V. V. Buryy, no. det. 36938) .

Figures

FIGURE 96. Taraxacum dilutum. A detail of flower heads and involucres (S 12-27574). Scale bar = 10 mm.