Besides the artificial perfume-materials already mentioned, but a few others are employed in perfumery, viz: _Cumarin_, _heliotropin_, _vanillin_, and _nitrobenzol_, or _oil of mirbane_. Another series of artificial perfume-materials, the so-called fruit ethers, have also been recommended for perfumery purposes. Although such products are sometimes used, their employment is not advisable, since they produce an irritating effect upon the bronchial tubes and respiratory organs, and frequently cause headache. _Cumarin._--The agreeable odor of new-mown hay is chiefly due to the sweet-scented vernal grass (_Anthoxanthum odoratum, L._). This grass contains an odoriferous substance, the _cumarin_. The latter is also found in many other plants; for instance, in the tonka bean (the seeds of _Dipterix odorata_), in the sweet woodruff (_Asperula odorata_), and, combined with melilotic acid, in the melilot (_Melilotus officinalis, Descr._). Cumarin forms small, colorless crystals of a silky lustre. It is very hard, cracks between the teeth, shows a smooth fracture, and sinks in water. It has a very agreeable aromatic odor, which, on rubbing the substance with the fingers, becomes like that of oil of bitter almonds, and has a bitter, warm, and pungent taste. When pure it melts at 152.6° F., but when containing fat, like that separated from tonka beans, at from 104° to 122° F. Its boiling point lies at 554° F.; it volatilizes, however, at far lower temperatures, diffusing an odor resembling that of oil of bitter almonds, and sublimating in white needles. It is soluble in alcohol, ether, acetic acid, fat, and volatile oils. Of cold water (59° F.) 400 parts are, according to Buchner, required for its solution, but of boiling water only 45 parts. Tonka beans are the ripe seeds of _Dipterix odorata_. They are much used in perfumery on account of their content of cumarin, and formerly constituted the initial point for its manufacture. In commerce two varieties are distinguished, viz., _Dutch tonka beans_, derived from _Dipterix odorata, Willd._, indigenous to the forests of Guiana, and _English tonka beans_, from _Dipterix oppositifolia, Willd._, indigenous to Cayenne.