​TONQUA BEAN. The Tonqua, Tonka or Tonquin bean, also called the coumara nut, is the seed of Dipterix odorala, a leguminous tree growing to a height of 80 ft., native of tropical South America. The drupe-like pod contains a single seed possessed of a fine sweet "new-mown hay" odour, due to the presence of coumarin (q.v.). Tonqua beans are used principally for scenting snuff and as an ingredient in perfume sachets and in perfumers' "bouquets."