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 Indigo) er a, 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 1 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 Polygonacece 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 oj Dyeing and Calico Printing , by W. Crookes, p. 447. 
2 Matieres Premieres Organiques, par Pennetier, p. 513. 
3 Ibid., p. 516. Bui. de la Societe Industrielle de Mulhouse, vol. xxviii, p. 
307. 
