Description from Flora of China
Shrubs, subshrubs, or perennial herbs, with cystoliths, usually spiny. Leaves opposite, petiolate. Inflorescences axillary cymes (sometimes secund or reduced to dense clusters), terminal spikes, or flowers solitary; bracts present or absent; bracteoles 2, sometimes becoming spinose. Calyx deeply 4-lobed; outer 2 lobes larger [anterior lobe sometimes 2-cleft]; inner 2 lobes smaller. Corolla funnel-shaped, usually large; limb 5-lobed (usually with upper lip appearing 4-lobed); lobes subequal, quincuncial in bud. Stamens [2 or]4 and didynamous, one pair usually greatly reduced and/or sterile; anthers 2-thecous; thecae ± equal in size, equally inserted, lacking basal appendages; staminodes 1 or 3, sometimes bearing very small anthers. Ovary with 2 ovules per locule; stigma 2-cleft or entire. Capsule substipitate or lacking a distinct basal stalk, subellipsoid to ovoid, 2-4-seeded; retinacula present. Seeds discoid, pubescent with appressed hygroscopic trichomes.
Barleria procumbens Loureiro (Fl. Cochinch. 2: 377. 1790) is not treated here because no material was available for study. Barleria lupulina Lindley is only cultivated in China and not treated here.
About 80-120 species: tropical regions of Africa and Asia, one species in tropical America; four species (one endemic) in China.
(Authors: Hu Jiaqi (胡嘉琪 Hu Chia-chi), Deng Yunfei (邓云飞); Thomas F. Daniel)