Coca.—Erythroxylon Coca, Lamarck.
The natives of Peru and of the neighbouring provinces, at least in the hot moist regions, cultivate this shrub, of which they chew the leaves, as the natives of India chew the leaves of the betel. It is a very ancient custom, which has spread even into elevated regions, where the species cannot live. Now that it is known how to extract the essential part of the coca, and its virtues are recognized as a tonic, which gives strength to endure fatigue without having the drawbacks of alcoholic liquors, it is probable that an attempt will be made to extend its cultivation in America and elsewhere. In Guiana, for instance, the Malay Archipelago, or the valleys of Sikkim and Assam, or in Hindustan, since both moisture and heat are requisite. Frost is very injurious to the species. The best sites are the slopes of hills where water cannot lie. An attempt made in the neighbourhood of Lima failed, because of the infrequency of rain and perhaps because of insufficient heat.[647]
I shall not repeat here what may be found in several excellent treatises on the coca;[648] I need only say that the original home of the species in America is not yet clearly ascertained. Gosse has shown that early authors, such as Joseph de Jussieu, Lamarck, and Cavanilles, had only seen cultivated specimens. Mathews gathered it in Peru, in the ravine (quebrada) of Chinchao,[649] which appears to be a place beyond the limits of cultivation. Some specimens from Cuchero, collected by Poeppig,[650] are said to be wild; but the traveller himself was not convinced of their wild nature.[651] D’Orbigny thinks he saw the wild coca on a hill in the eastern part of Bolivia.[652] Lastly, M. André has had the courtesy to send me the specimens of Erythroxylon in his herbarium, and I recognized the coca in several specimens from the valley of the river Cauca in New Granada, with the note “in abundance, wild or half-wild.” Triana, however, does not admit that the species is wild in his country, New Granada.[653] Its extreme importance in Peru at the time of the Incas, compared to the rarity of its use in New Granada, seems to show that it has escaped from cultivation in places where it occurs in the latter country, and that the species is indigenous only in the east of Peru and Bolivia, according to the indications of the travellers mentioned above.
Dyer’s Indigo.—Indigofera tinctoria, Linnæus.
The Sanskrit name is nili.[654] The Latin name, indicum, shows that the Romans knew that the indigo was a substance brought from India. As to the wild nature of the plant, Roxburgh says, “Native place unknown, for, though it is now common in a wild state in most of the provinces of India, it is seldom found far from the districts where it is now cultivated, or has been cultivated formerly.” Wight and Royle, who have published illustrations of the species, tell us nothing on this head, and more recent Indian floras mention the plant as cultivated.[655] Several other indigoes are wild in India.
This species has been found in the sands of Senegal,[656] but it is not mentioned in other African localities, and as it is often cultivated in Senegal, it seems probable that it is naturalized. The existence of a Sanskrit name renders its Asiatic origin most probable.
Silver Indigo—Indigofera argentea.
This species is certainly wild in Abyssinia, Nubia, Kordofan, and Senaar.[657] It is cultivated in Egypt and Arabia. Hence we might suppose that it was from this species that the ancient Egyptians extracted a blue dye;[658] but perhaps they imported their indigo from India, for its cultivation in Egypt is probably not of earlier date than the Middle Ages.[659]
A slightly different form, which Roxburgh gives as a separate species (Indigofera cærulea), and which appears rather to be a variety, is wild in the plains of the peninsula of Hindustan and of Beluchistan.
American Indigoes.