Plant erect, pubescent perennial herb; stem much branched from the base; leaves simple, opposite, exstipulate, ovate-lanceolate or oblong-lanceolate, serrate, glabrous above, puberulous along the nerves beneath; flowers numerous in a cluster, in racemes or verticillasters, 6-8 flowers in a whorl; calyx oblong-campanulate, glabrous within, densely tomentose outside; corolla violet with white veins, hairy throat, bilipped, upper lip bilobed, hairy outside, lower lip trilobed; stamens 2, anthers 1 celled, filaments jointed near the base; ovary 4-celled, 4-ovuled, style hairy, gynobasic, stigma bifid; capsule minute.