柞木 zuo mu

Croton congestus Loureiro, Fl. Cochinch. 2: 582. 1790 ["congestum"]; Apactis japonica Thunberg (Nov. Gen. 66. 1783); Casearia subrhombea Hance; Flacourtia chinensis Clos; F. japonica Walpers; Hisingera japonica Siebold & Zuccarini, nom. illeg. superfl.; H. racemosa Siebold & Zuccarini; Myroxylon japonicum (Thunberg) Makino; M. racemosum (Siebold & Zuccarini) Kuntze; Xylosma apactis Koidzumi, nom. illeg. superfl.; X. congesta var. caudata S. S. Lai; X. congesta var. pubescens (Rehder & E. H. Wilson) Chun; X. japonica (Thunb.) A.Gray ex H.Ohashi, Fl. Japan 2C: 160. 1999; X. japonica var. pubescens (Rehder & E. H. Wilson) C. Y. Chang; X. racemosa (Siebold & Zuccarini) Miquel; X. racemosa var. caudata (S. S. Lai) S. S. Lai; X. racemosa var. glaucescens Franchet; X. racemosa var. pubescens Rehder & E. H. Wilson; X. senticosa Hance.

Shrubs or small trees, evergreen, 4-15 m tall; bark brown-gray; branches spiny when young, unarmed when old, glabrous or puberulous. Stipules subulate, minute, ca. 0.3 mm, glabrous, in dried material dark brown or blackish, caducous or persistent for some time; petiole short, 2-5 mm, glabrous to quite densely pubescent with spreading hairs; leaf blade broadly ovate to ovate-elliptic, 3-8 × 2.5-3.5 cm, leathery, often glaucous below, both surfaces glabrous, or scarcely pubescent along veins below, lateral veins 3 or 4(or 5) pairs, base usually obtuse to rounded, less often acute, margin serrate, apex acute, tip usually acuminate, acumen 5-10 mm. Inflorescence axillary, racemose, short, 0.5-2 cm; rachis densely pubescent, hairs spreading, short; flowers yellowish. Pedicels very short, 1-3 mm in flower and fruit, pubescent. Bracts ovate to narrowly lanceolate, 1-2.5 mm, abaxially pubescent, ciliate, caducous or persistent. Sepals 4-6, broadly ovate with rounded apex, or orbicular, 1-2 mm, outside ± pubescent, inside glabrous, ciliate. Staminate flowers: stamen filaments long, eventually extending to ca. 3 mm; anthers ellipsoid, minute, ca. 0.2 mm, connective usually not projected beyond thecae; disk consisting of several, small, glabrous, closely set or connate glands. Pistillate flowers: disk annular, undulate; ovary ovoid, ca. 4.5 mm; placentas 2; styles 2, very short (to 0.5 mm) to nearly absent, joined in basal half. Berry dark red to black (black when dried), globose, 4-5 mm in diam.; calyx and disk persistent at least while fruit attached to plant; styles persistent. Seeds 2 or 3, reddish brown when dry, ovoid, flattened on one side by mutual pressure, 4-5 mm, completely covered in a thin membranous darkly streaked sheath. Fl. Jul-Nov, fr. Aug-Dec.

Forest margins, thickets on hills, plains, surrounding villages; 500-1100 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [India (rare), Japan, Korea].

The varieties Xylosma racemosa var. glaucescens and X. racemosa var. pubescens are not upheld here. The characters used to distinguish them, glaucescence of the leaves, or hairiness of branchlets and petioles and venation of the abaxial leaf surface, were found to vary continuously throughout the species.

For Xylosma senticosa only three specimens (including the type) were available. Of these, Hance 7437 (type; K) and a specimen numbered "9204" (collector illegible; K) were collected from Victoria Peak, Hong Kong. The third specimen, Ford 579 (K), possibly a cultivated specimen, is also annotated "Victoria Peak." Between them, the specimens bear staminate or structurally bisexual flowers. All are similar to X. congesta but differ in the following combination of characteristics: leaves very small (1.5-3 cm), flowers sometimes structurally bisexual, sepals glabrous outside (margin ciliate), pedicel above the articulation glabrous, lower part of pedicel and inflorescence rachis glabrous or sparsely hairy, anther with connective projected as a fleshy, triangular appendage. After one of us (Yang) examined extensive gatherings of Xylosma from Hong Kong at PE, the inclusion of X. senticosa Hance within X. congesta was recommended.

After publication of this family in FOC 13, the Flora of Japan (1999) treated this as Xylosma japonica based on Apactis japonica Thunberg.