C. perfoliata: annual; stems erect, stiff, 1/2-2 feet high, pale glaucous green; leaves in a spreading tuft, elliptic-oblong, those of the stem in distant pairs, perfoliate; flowers bright yellow, in terminal cymes, the corolla nearly rotate. - Yellow-wort. - Dry pastures and waste places, in limestone districts. Fl. July, August.