304 ECONOMIC BOTANY. 



292. Anchusa linctoria, of the Borrage family (Borragin- 

 aeece), yields the red dye called Alkanet. The plant is 

 perennial, and has pretty blue flowers. It is a native of 

 Southern Europe, and extensively cultivated for the roots, 

 which are yellowish within, and dark violet on the surface. 

 The important constituent and coloring matter is Anchu- 

 sin, a resinous, purple-red substance. Alkanet is much 

 used in coloring fats, alcohol, and varnishes. An alcoholic 

 extract is used in dyeing linen, cotton, and silk; for dyeing 

 goods violet they must be previously prepared with alum 

 mordants, and for coloring gray the fabrics must have 

 been prepared with iron mordants. 



293. Curcuma longa, a member of the Banana family 

 (Sfyitaminece), is a native of Southern Asia, and is culti- 

 vated in India, Ceylon, Java, the West Indies, etc. Many 

 different varieties have arisen under cultivation, which 

 furnish the dye Turmeric in varying qualities. The rhi- 

 zome is tuberous, and from it arise leaves, some being 

 roundish, others narrow. It is heavier than water, and 

 yellow or orange in color. The taste is somewhat pungent 

 and spicy, the odor aromatic. The coloring matter resides 

 both in the cell-walls and also as an amorphous mass 

 within the cells. Its most important constituent is Cur- 

 cumin, in the shape of prismatic crystals ; it is soluble in 

 ether and alcohol. Turmeric (the yellow rhizome) is 

 used in dyeing paper, wood, and leather, and in coloring 

 varnishes. It is much used in cookery, also in medicine. 

 Turmeric paper, or unsized paper colored with a decoction 

 of Turmeric, is used in the chemical laboratory as a test for 

 free alkali, which turns it brown. 



294. The Ginger-plant, Zimiher officinale (family Sd- 

 tamineai), has been cultivated, from time immemorial, in 



