234 MEDICAL BOTANY. 



They owe these properties to the presence of Cytisine, which appears to act 

 with much power on the cerebro-spinal system. 



Indigofera. — Linn. 



Calyx 5-cleft, lobes obtuse. Vexillum roundish, emarginate. Carina on either side, 

 near the base, producing a subulate, spreading spur. Stamens diadelphous. Legume 

 linear, rather small, terete or quadrangular. 



This vast genus, of upwards of a hundred species, is composed of herba- 

 ceous and suffruticose plants, with simple or pinnate leaves, furnished with 

 small stipules. They are all more or less tomentose or hirsute, and have 

 purple, blue, or white flowers. The greatest number of them are natives of 

 Africa and India ; a few are indigenous to the United States. Many of them 

 furnish a peculiar product, well known as Indigo, the preparation of which 

 was known to the aborigines of this continent at the time of the discovery ; 

 and it is remarkable, as is observed by Sonnini, that Nil or anil is one of 

 the American names for the Indigo plant, which is also called Nili by the 

 Arabs. Although many species furnish Indigo, the best, or Bengal, is pro- 

 cured from the I. tinctoria. 



I. tinctoria, Linn. — Leaflets 4 — 5 pairs, ovate, somewhat pubescent beneath ; racemes 

 shorter than the leaves ; legumes terete, arcuated, deflexed. 



Linn., Sp. PL 1061; Lam., Diet. iii. 245; Lindley, Fl. Med. 242; 

 De Candolle, Prod. ii. 224. 



Common Name. — Indigo Plant. 

 Foreign Name. — Indigotier, Fr. 



Description. — A shrub about two feet in height, with 

 spreading, sub-flexuose branches, which are angulose, and 

 appressed-puberulous near their extremities. Leaves pin- 

 nate. Leaflets 4 — 5 pair, with an odd one, petiolated, ellip- 

 tic, acute at base, mucronate at tip, with an appressed pu- 

 bescence beneath. Stipules small and subulate. Racemes 

 axillary, not as long as the leaves. Flowers pedicellate, with 

 minute subulate bracts. Calyx 5-toothed, the two upper 

 wider apart than the others. Flowers of a greenish colour, 

 marked with vermilion red. Standard ovate, mucronate, mi- 

 nutely ciliate, and pubescent externally. Wings shorter than 

 the keel, which is concave, greenish, minutely ciliated. Le- 

 I. tinctoria. "" gume more than an inch in length, arcuated, terete, pube- 



scent, containing ten seeds. 



Several species of Indigofera are cultivated, but the I. tinctoria is that 

 grown in India and very extensively in South America, the Guatimala plant, 

 I. disperma, being considered by De Candolle as a variety of it. Besides this, 

 the /. anil, I. caroliniana, and I. argentia, are also used, the two latter in 

 the United States. The I. tinctoria abounds most in colouring principles, 

 and is therefore the one generally selected for cultivation. 



Indigo is a rich blue substance, light and friable, tasteless, almost devoid 

 of smell, of a smooth fracture, insoluble in water or alcohol, but dissolved by 

 sulphuric o* nitric acid. It consists of indigotin, or indigo blue, indigo brown, 

 indigo red, and a gelatinous substance. It is procured in three different modes ; 

 by fermentation, which was the most general plan, by scalding, and by the 

 dry process; which latter is becoming much used in India, and is said to 

 afford the best product, whilst it is not so injurious to the health of those en- 

 gaged in the manufacture. (See Encyclop. Amer., Art. Indigo.) In what- 



