P. orbiculare: stems simple, erect or slightly decumbent, 1/2-1 1/2 foot high; radical leaves ovate, cordate, on long stalks, those of the stem narrow-oblong or lanceolate, the upper ones sessile; flowers deep blue, in a globular terminal head, surrounded by a few short, broadly lanceolate bracts. - Chalk downs of southern England. Fl. August.