var. angustifolia Koidzumi; P. japonica f. ovatifolia Chodat; P. luzoniensis Merrill; P. sibirica Linnaeus var. japonica (Houttuyn) Ito; P. taquetii H. Léveillé.
Herbs perennial, 15-20 cm tall. Stems and branches erect or decumbent, brown-green or green, longitudinally angular, curved pubescent. Petiole ca. 1 mm, pubescent; leaf blade ovate or ovate-lanceolate, rarely linear-lanceolate, 1-2.3(-3) cm × (3-)5-9 mm, thickly papery or subleathery, both surfaces glabrous or pubescent, midvein raised abaxially, impressed adaxially, lateral veins 3-5 pairs.
Three new xanthones, 1,3-dihydroxy-2,5,6,7-tetramethoxyxanthone (1), 3-hydroxy-1,2,5,6,7-pentamethoxyxanthone (2), and 3,8-dihydroxy-1,2,6-trimethoxyxanthone (3), together with two known compounds were isolated from the roots of Polygala japonica Houtt. Their structures were determined on the basis of spectroscopic data.