PLANT ANALYSIS AS AN APPLIED SCIENCE 203 



Total value madder and alizarin : 



1884 $421,100.00 



1885 484,630.00 



Many species of plants grown in different parts of the world, 

 but especially the Indigofera, yield a glucoside called indican, 

 which, under the influence of dilute mineral acids and certain 

 ferments, breaks up, yielding indigo blue and a substance re- 

 sembling glucose. 



"Indigo * has undoubtedly been known in Asia from a very 

 remote period of antiquity, since there exist, in very ancient 

 records written in the Sanskrit language, descriptions of its 

 mode of preparation mainly not different from the methods 

 yet in use." The manner of cutting the plant and extracting 

 the indigo is not the same in all countries. In India, the plants 

 are grown from seeds which are sown in the fall and spring, 

 according to the kind of plant. As soon as the young plants 

 are sufficiently forward they are replanted in regular rows. 

 The flower buds are pulled off before they are fully developed, 

 experience having taught that by so doing the leaves of the 

 shrub become larger and yield more indigo, the coloring-matter 

 being chiefly present in the leaves. 



The indigo of commerce is a blue dyestuff extracted by 

 fermentation. Other plants 2 used occasionally for the ex- 

 traction of indigo are more frequently employed directly in 

 dyeing; they belong to the Polygonacea family. These plants 

 are from India, China, Central Africa, and South America, 

 and they can be acclimated in all warm countries. In the 

 mode of indigo manufacture 3 two processes are employed. In 

 the one the dry leaves are used, in the other the green leaves. 

 This is the one in most common use. When the plant begins 

 to flower it is cut down at about six inches from the ground 

 and carried to the steeping vats with as little delay as possible, 

 strewn horizontally in the vats, and pressed down by means 



1 Hand-Book of Dyeing and Calico Printing, by W. Crookes, p. 447. 



2 Matieres Premieres Organiqites, par Pennetier, p. 513. 



3 Ibid.) p. 516. Bui. de la Societe Industrielle de Mulhouse, vol. xxviii, p. 



307- 



