348 The N.Z. Journal of Science and Technology. [Nov. 
Regarding the portion of the plant which yields the dyes of commerce 
the greatest diversity prevails. In the indigo-plant it is the leaves which 
chiefly yield the dye, the crop being therefore valuable in proportion to the 
amount of leaves ; weld is obtained from the leaves, madder from the 
roots, alkanet from the cortical part of the roots, turmeric from under¬ 
ground stems, quercitron from the bark of a tree, and fustic, logwood, and 
Brazil wood from the wood of trees of considerable size ; Persian berries 
from a fruit, annatto from the arils and seed covering of the fruit, catechu 
from various exudations, saffron from the stigmas of flowers, and safflower 
from the petals. 
It may be useful to summarize briefly the natural vegetable colouring- 
matters in commerce at the present time. 
Indigo, the product of a number of species of the genus Indigofera, is the 
most important of vegetable and artificial dyestuffs. Its cultivation suffers 
severely from the competition of the synthetic product, but the war has 
induced an enhanced demand for the natural indigo, the result being that 
the land under indigo crop was five times greater in 1917 than it was at 
the beginning of the war. The indigo-planter is, moreover, studying the 
plant scientifically, and by experiments in breeding and hybridizing has 
materially increased production. W. A. Davis,* Indigo Research Chemist 
to the Government of India, reports that the total world's market of 
natural and synthetic indigo before the war considerably exceeded five 
millions sterling, a value not far short of that of all other artificial 
organic dyes put together. He considers that, provided certain improve¬ 
ments in actual practice can be effected—and they are clearly possible— 
the natural indigo will be able to put up an interesting fight with the 
synthetic dye. 
Madder, the cortex of the root of Rubia tinctorum, a perennial plant, 
is largely grown on the Continent of Europe. In the year 1868 the world 
grew 70,000 tons of cultivated madder, but by the synthesis of the colour¬ 
ing principle, alizarin, in that year the natural dyestuff has been entirely 
displaced for calico-printing in Europe and America. Madder is now used 
only in wool-dyeing. It must be a fairly expensive crop to grow, as the 
plant is not harvested until the third year of its growth. In Turkey and 
the East, where they have more time, it is still used for dyeing the famous 
Turkey red, and it is usual to allow the roots to remain in the ground for 
five or even seven years. In spite of the chemist’s art in making artificial 
dyes, Great Britain still dyes all the scarlet cloth required in its soldiers' 
uniforms with cochineal, and France still uses for its uniforms cultivated 
madder. Cheese is still coloured in New Zealand and elsewhere with 
arnotto, or annatto, produced from the arils or pulpy matter surrounding 
the seeds of Bixa Orellana , a tropical small tree from which the American 
Indians made almost their only clothing — a body-paint. 
Sweetmeats, medicines, and pomades are still coloured with alkanet 
derived from the roots of Anchusatinctoria, a cultivated boraginous 
plant. 
Large quantities of turmeric from Cucuma tinctoria tubers cultivated in 
India and the East are still used in the direct dyeing of wool, cotton, and 
silks, although the colour is fugitive to light, soap, and alkalies. Turmeric* 
is used in the preparation of curry-powder, and in the laboratory is a useful 
indicator, especially for boric acid. 
* Ag. Jour. India . No. 13, p. 32, 1918. 
