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FOC | Family List | FOC Vol. 20-21 | Asteraceae | Ixeridium

5. Ixeridium dentatum (Thunberg) Tzvelev, Fl. URSS. 29: 392. 1964.

小苦荬 xiao ku mai

Prenanthes dentata Thunberg in Murray, Syst. Veg., ed. 14, 715. 1784; Ixeris dentata (Thunberg) Nakai; I. thunbergii A. Gray; Lactuca dentata (Thunberg) C. B. Robinson; L. thunbergii (A. Gray) Maximowicz; Youngia dentata (Thunberg) Candolle.

Herbs 20-50 cm tall, perennial. Rhizomes shortly oblique, with fibrous roots. Stems solitary or few, slender, erect, branched from base or higher up, glabrous, sparsely leafy. Basal leaves crowded, usually present at anthesis, narrowly oblanceolate, narrowly elliptic, or elliptic, 4-15 × 1-3 cm, undivided or pinnatipartite, base attenuate into a winged or unwinged petiole-like portion, margin entire or with slender or very fine teeth especially in basal half, apex acute to obtuse and mucronate; lateral lobes (if present) 1-3 pairs, on basal half of leaf, narrowly triangular. Stem leaves ± lanceolate, undivided, base usually expanded and amplexicaul or auriculately clasping, margin entire or with slender or very fine teeth especially in basal half. Synflorescence corymbiform, with some to many capitula. Capitula with 5-7[-11] florets; peduncle capillaceous. Involucre cylindric, 7-8 mm. Phyllaries abaxially glabrous; outer phyllaries broadly ovate, ca. 1.5 × 1 mm; inner phyllaries 5[-8], apex acute. Florets yellow [or rarely white]. Anther tube and style greenish to blackish upon drying. Achene brown, fusiform, 3-3.5 mm, apex attenuate into a slender ca. 1 mm beak. Pappus straw-colored, 4-5 mm. Fl. and fr. Apr-Aug. 2n = 14, 21, 28.

Forests on mountain slopes, moist places, fields; 300-1100 m. Anhui, Fujian, ?Guangdong, ?Hebei, ?Heilongjiang, Hubei, Jiangsu, Jiangxi, ?Jilin, ?Liaoning, Shandong, Zhejiang [Japan, Korea, E Russia].

Ixeridium dentatum forms a polyploid complex, and several subspecies have been described to classify the diversity within this complex (Pak & Kawano, Mem. Fac. Sci. Kyoto Univ., Ser. Biol. 15: 42-45. 1992; Yahara in Iwatsuki et al., Fl. Japan 3b: 18-19. 1995, under Ixeris). In China only Ixeridium dentatum subsp. dentatum occurs; its distributional range has not been fully established yet. It has sometimes been confused with I. laevigatum, which is, however, clearly distinguished from I. dentatum subsp. dentatum through the involucres with 8 (instead of 5) inner phyllaries, 8-11 (instead of 5-7) florets per capitulum, and never (instead of usually) clasping stem leaves.


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