20. Lasianthus japonicus Miquel, Ann. Mus. Bot. Lugduno-Batavi. 3: 110. 1867.
日本粗叶木 ri ben cu ye mu
Shrubs, 1-2 m tall; branches and branchlets glabrous or subglabrous to sparsely strigose on young branches. Petiole 3-10 mm, sparsely strigillose to strigose or subglabrous; leaf blade leathery or papery, lanceolate, lanceolate-oblong, or oblong, 9-15 × 2-3.5 cm, glabrous adaxially, glabrous to strigose or hirtellous abaxially, especially on lateral veins and nervules, base acute to obtuse, apex cuspidate or cuspidate-acuminate to long caudate; lateral veins 5-7 pairs or numerous; nervules reticulate; stipules generally persistent, triangular, 1-3 mm, glabrous to minutely hirsute to strigillose. Inflorescences congested-cymose, pedunculate to subsessile, densely strigillose; peduncle 1-2 mm; bracts 0.2-1 mm. Flowers sessile or subsessile. Calyx strigillose to glabrescent; hypanthium portion campanulate, 1-1.5 mm; limb 1-2 mm, 4- or 5-dentate; teeth short to well developed, linear. Corolla 13-14 mm at anthesis, glabrous outside or sometimes puberulent on lobes, villous inside; tube 9-10 mm; lobes 4 or 5, spatulate, 4-4.5 mm. Fruit globose, 5-6 mm in diam., glabrous; pyrenes 4 or 5. Fl. Apr-May, fr. Jun-Oct.
Forests, shaded and wet places; 200-2300 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [NE India, S Japan (Kyushu, Ryukyu Islands, Shikoku), Laos, N Vietnam].
This species is commonly collected in China. The leaf margin is often finely irregular, not crisped but actually undulate parallel to the looping tertiary venation that is near it. The leaves generally flush in a characteristic fashion, elongating but remaining rolled up and narrow, and are covered with notable sericeous pubescence on the exposed lower surfaces of the midrib and principal veins. This pubescence is often deciduous, leaving the mature lower leaf surface glabrous.
Lasianthus japonicus is a widely distributed species from E Asia to the Himalaya. Lasianthus japonicus subsp. japonicus occurs in SE China to Japan, below 1800 m, and basically in the Sino-Japanese floristic region delineated by C. Y. Wu (Bull. Univ. Mus. Univ. Tokyo 37: 1-9. 1998). Lasianthus japonicus subsp. longicaudus occurs in SW China and NE India in the Himalaya, at 1000-2300 m, i.e., in the Sino-Himalayan floristic region of Wu. They are a typical vicariant pair of subspecies. It may be surprising that L. lucidus var. caudisepalus from Assam, NE India, is found to be conspecific with L. japonicus subsp. japonicus. However, the geological history of E Asia gives an explanation. The formation of the vicarious distribution patterns of the Sino-Himalayan and Sino-Japanese regions is supposed to be related to the uplift of Himalaya in the Tertiary. Lasianthus japonicus subsp. longicaudus could have differentiated with the uplift of Himalaya becoming an altitudinal vicariant taxon of L. japonicus.
