Mitella acerina Makino

M. Wakabayashi, 2006, Tiarella and Mitella, Flora of Japan, Volume 2 b: Angiospermae-Dicotyledoneae: Archichlamydeae (b), Kodansha, pp. 70-75 : 71-72

3. Mitella acerina Makino

in Bot. Mag. Tokyo 16: 159 (1902).

Japanese name: Momiji-charumeru-so.

Dioecious perennial herbs. Rhizomes long creeping, hypogaeous, stoloniferous, with scales or small leaves.

Radical leaf blade widely ovate, deeply cordate, acute to acuminate, 4-12 cm long, 4-10 cm wide, acutely 5-7-lobed, incised and toothed, upper surface sparsely pilose, lower surface glabrous, light green; petiole 15-30 cm long, glabrous, with a fused axillary stipule at base; stipules scarious, entire. Flowering stems 20-40 cm tall, erect, densely short glandular hairy, glabrous near base. Inflorescences racemes, compactly many-flowered. Flowers April to May; pedicel 1-3 mm long, minutely glandular. Calyx tube broadly obconical, sparsely glandular; calyx lobes 5, triangular-ovate, obtuse, nearly glabrous on both surfaces, ca. 1 mm long, obliquely spreading and reflexed, greenish or greenish brown. Petals 5, 3-5-pinnatiparted, minutely glandular, ca. 3.6-4 mm long, spreading or reflexed, brownish purple; pinnae slender, spreading or obliquely ascending. In male flowers, stamens 5, alternate calyx lobes, adjacent to base of petals, ca. 0.8 mm long; anthers ovate, cordate, 2-tuberculate apically, ca. 0.7 mm long, yellow; disc prominent, flat, pale brownish; ovary inferior; ovules very small, abortive; styles 2, erect, 0.2 mm long; stigmas rather thickened, not lobed, ca. 0.5 mm across. In female flowers, stamens 5, alternate calyx lobes, adjacent to base of petals, ca. 0.4 mm long; anthers ovate, cordate, 2-tuberculate apically, ca. 0.35 mm long, without pollen, pale brownish; disc prominent, flat or somewhat convex, greenish; ovary inferior; ovules developed; styles 2, erect, 0.2 mm long; stigmas strongly thickened, not lobed or indistinctly 2-lobed, ca. 0.7 mm across. Seeds oblong, ca. 1 mm long, scabrous, without papillae, greenish. Chromosome number: 2n = 28 (Wakabayashi 1973). Japan: C. Honshu (Japan Sea side area of Kinki Dist.; Fukui, Kyoto, Shiga Pref.). Wet places along streams in lowlands. Endemic.

Icones: Nakai & Honda, Nov. FI. Jap. 3: f. 7 (1939); Kitamura & Murata, Herb. PI. 2: t. 35 298; Satomi in J. Geobot. (Kanazawa) 23(3): 33 (1976); Satake et al., Herb. PI. 2: photo. 152 1 & 2.