4. Aesculus hippocastanum Linnaeus, Sp. Pl. 1: 344. 1753.
欧洲七叶树 ou zhou qi ye shu
Hippocastanum vulgare Gaertner.
Trees to 30 m tall, to 2(-5) m d.b.h. Branchlets brown villous when young. Petiole 8-20 cm, glabrous; leaf blade 5-7-foliolate; leaflets sessile, abaxially green, oblanceolate, 10-25 × 5-12 cm, abaxially glabrous or with sparse whitish hairs, ferruginous tomentose (often densely so) at base and in axils of lateral veins, base cuneate, margin crenate-serrate with teeth crenulate-serrulate, apex acuminate to subcaudate; lateral veins in 18-25 pairs. Inflorescence glabrous or matted ferruginous villous and shortly whitish tomentose (whitish hairs mostly on pedicels); peduncle 2.5-5 cm; thyrse conic or cylindric-conic, 10-30 cm, 6-10 cm wide at base; branches 2.5-5 cm, 4-12-flowered; pedicels 3-6 mm. Calyx 5-6 mm, abaxially tomentose. Petals 4 or 5, white, with red spots and a yellow (later brown) claw, equal, ca. 11 mm, abaxially sparsely whitish tomentose or glabrous. Stamens 5-8, 10-20 mm; filament villous; anther 1-1.3 mm. Style glabrous except at base. Capsule brown, globose or subglobose, 2.5-4 × 2.5-6 cm excluding prickles, prickly; prickles subulate, slightly curved, to 10 mm; pericarp 3-5 mm thick after drying. Seeds 1-3(-6), glossy chestnut brown, subglobose, 2-4 cm; hilum pale brown, occupying 1/3-1/2 of seed. Fl. May-Jun, fr. Sep.
Introduced to China, cultivated. Shandong (Qingdao), Shanghai [native to SE Europe (Albania, Bulgaria, Greece, Former Yugoslavia); widely introduced elsewhere].
This species is easily recognized by its prickly capsule.