The plants which are known to furnish indigo are quite numerous, being not less than sixty; they do not all belong to the same family, and none of them contain the coloring principle already formed. The most important belong to the leguminous family, from which most of the vegetable dyes are derived, and to the genus _indigofera_. The species cultivated and most esteemed are _Indigofera tinctoria_, _I. disperma_, _I. anil_, _I. argentea_. [Illustration: Drawing of the Indigofera tinctoria plant] The principal source of the indigo of commerce is the _Indigofera tinctoria_. The accompanying figure is a correct representation of the plant, and we may dispense with a description of its botanical characters, observing only that the plant has a half woody stem, and rises to the height of from three to five feet. The plants exhale a strong odor towards evening in the fields where they are cultivated. The leaves have a disagreeable taste, and rapidly putrefy in water. The plant originated in Campaja, or Guzerat, but is cultivated in Hindostan, China, Java, and in the East Indies generally. It was carried by the Spaniards to South America and the West Indies, and it can be acclimated in all hot countries. The _Indigofera argentea_, or indigo plant of Egypt, furnishes the indigo produced in that country and Arabia. The culture of the plant and the production of commercial indigo is carried on a vast scale in Lower Bengal. We have before us a large map, placed at our disposal by an India merchant of Boston, showing the location of each of the hundreds of factories of that important centre of production. These factories have been developed by British enterprise; and India thus receives some slight compensation for the ruin of her cotton manufacture by the same influence. The propagation of the indigo plant in that country is made by sowing in a thoroughly tilled silico-argillaceous soil. The seed of the plant is sowed annually in the spring or autumn, according to the variety used, some germinating more slowly, and requiring to remain in the ground longer than others. The time of putting in the seed is also governed by the nature of the soil and its position in respect to neighboring rivers. In the lowlands subject to inundations, the indigo ought to be all cut at the period of the rains and inundations, which would destroy the crop in a brief time. Besides, during the rainy period the planter has at his disposal sufficient water to commence his operations of fabricating the indigo, which is the suitable time for beginning the cutting of the plant. The time of cutting the indigo plants is therefore regulated by the elevation of the land and danger from floods. The high lands are always sowed several weeks after those subject to inundations.