Virginia, mixed, collected in June, gave A nearly white precipitate. „ „ „ July, „ A decidedly yellowish- white precipitate. „ _R. copallina_ „ August, „ A dirty- yellow precipitate. „ _R. glabra_ „ „ „ A very dirty- white precipitate. Fredericksburg, mixed „ „ „ A dirty- yellow precipitate. Sicilian „ „ „ A slightly yellowish- white precipitate. For the purpose of tanning white and delicately coloured leathers, therefore, the collection should be made in June; while for tanning dark-coloured leathers, and for dyeing and calico-printing in dark colours, where the slightly yellow shade will have no injurious effect, the collection may be made in July. It appears that for all purposes, the sumach collected after the 1st of August is inferior in quality. Experimental results as regards percentage of tannin obtained by collecting sumach at different seasons showed:-- Per Cent. of Tannic Acid. Virginia, mixed, collected in June, gave 22·75 „ „ „ July, „ 27·38 „ _R. glabra_ „ August, „ 23·56 „ _R. copallina_ „ „ „ 16·99 Sicilian, _R. coriaria_ „ „ „ 24·27 It is evident, therefore, that in order to secure the maximum amount of tannic acid, the sumach should be collected in July, but the colouring matter of the leaves has an important influence upon the value of the product. The leaves of the upper extremities of the stalks are always richer in tannic acid than those of the base; and the increase of age of the plant is accompanied by a general diminution of this acid.