338 LEGUMINOS.E PRODUCING TANNING MATTERS AND DYES 



oxidized by contact with the atmosphere, yielding indigotiHj the blue 

 colouring matter. (See A. Haller, " L'indigo naturel et I'indigo 

 artificiel.") 



Colouring matter may be obtained from other indigo plants, such 

 as Indigofera -pseudo-tinctoria^ I. dis-per))ia^ I. Jiirsiita_, I. angustifoUa, 

 I. trifoliata, I. sericea, I. cytiso'ideSj I. glabra^ I. glauca, I. Atiilj &c. 

 These are less cultivated. 



hidigofera Anil is cultivated in Java and the Sunda Isles; /. tinc- 

 toria is very common in India; the Guatemala indigo plant, which 

 has been introduced into Java, is /. oUgosfernia^ and that of Natal is 

 /. leptostacJiya. I. ere eta is also found in Java and Natal. 



The colouring matter of the indigo plant was known in the Middle 

 Ages. Marco Polo gave a description of it, although a very short one, 

 in i2g8. The Russian traveller Athanasius Nikitin spoke, in 1468 of 

 Cambay, where the indigo plant grows. Garcia de Orta (1563) gives 

 a summary of the cultivation and manufacture of indigo. In Pere 

 Labat's " Voyage aux Isles de I'Amcriciue " occurs a long and inter- 

 esting account of the manufacture of indigo. Similarly, during the 

 last eight centuries, this colouring matter has attracted the attention 

 of numerous authors. 



The use of indigo dates back a considerable time. Cossigny cjuotes 

 an extract from the "Memoirs of the Societe dWgriculture de Paris" 

 for the year 1789, in which the citizen Moreau de St. Mery states that 

 in Dondon and many other parts of the colony the indigo plantations 

 had been abandoned, and that a similar state of affairs was threatening 

 Bourbon. 



At this period the consumption of indigo in France had increased 

 owing to the clothing of the Garde-nationale and the Republican 

 troops in uniforms of this colour, and also because the colour was 

 fashionable. 



The chief centres of indigo production are British India, the 

 Philippines, Siam, China, Japan, Natal, New Granada, Venezuela, 

 Mexico, &c. 



The value of the total production of indigo is from about ;<!2,5oo,ooo 

 to /!3, 000, 000 per annum. 



In 1878 von Boeyer first solved the problem of artificial indigotin. 

 The production has recently been put on a more economic footing. 

 Two methods are in use : one has naphthalene as its basis, and the 

 other toluene, both extracted from coal tar. 



The indigo plant needs to be cultivated under good conditions. 

 The date of sowing varies in different countries, the seeds usually 

 being planted at the beginning of the winter season. By using 

 selective methods plants with large yields iiave been obtained. In 

 India, and also other countries, attention has only been directed to 

 the most paying varieties. 



Indigofera tinetoria is a native of Gujerat and has become acclima- 

 tized in all warm countries; but, as has already been remarked, in 

 every country there is one particular variety which takes precedence 

 over the remainder owing to its cultural reciuirements and to its better 

 vield. 



