To facilitate study, this order has been divided, one of the subdivisions being the sub-order Aurantieae (see below). The rueworts are remarkable for yielding acrid and resinous principles and volatile oil. Ruta montana, growing in Spain, is so extremely acrid that it raises pustules on the skin of those who gather it. The peduncles and flower of the European Dittany are so laden with volatile oil that the plant ignites at the approach of a lighted candle.
A Manual of Organic Materia Medica and Pharmacognosy, 1917, was written by Lucius E. Sayre, B.S. Ph. M.