308 ILLUSTRATIONS OF THE BOTANY OF { Polemoniacee. 
layas, and also in Kunawur, with a species allied to C. Europea. Convolvulus arvensis, 
found almost every where, occurs both in the plains and mountains of India. 
The Convolvulacee are well known for the purgative properties of the roots of 
many of the family, as of Jalap, Scammony, &c. Convolvulus panduratus is substituted 
in the United States for the former; so, in India, Ipomea Turpethum, toorbud of the 
Arabs, supposed to be a corruption of the Sanscrit trivrit, Hindee nusot, is accounted 
a powerful cathartic, and by Dr.Wallich an excellent substitute for jalap, (v. Gordon, 
in Roxb. FI. Ind. ed. Wall. 2. p. 58) ; so the seeds of Jpomea cerulea, hub-ool-nil, kala 
dana, are accounted purgative in India, as are several others of this family. The 
annual shoots not having secreted the due proportion of resin, are inert, and even 
edible; as the stalks of C. edulis and repens. The tubers of Batatas edulis, or sweet 
potatoe, have long been employed as food. 
Convolvulus Scammonia, of which the dried resinous juice forms scammony, sukmoonya 
of the Arabs, is chiefly produced near Smyrna and Aleppo; but only inferior kinds 
find their way to India, though there is little doubt that it might be produced of the 
best quality in Northern India. The Jalap exported from Vera Cruz was supposed to 
be produced in that neighbourhood, or in that of Xalapa, by Jpomea macrorhiza of 
Michaux. But it was known to Humboldt (New Spain. vol. iii. p. 36), and also to 
Dr. Coxe (v. Thomson. Elem. of Mat. Med. ii. p. 289), to be the produce of a different 
plant. The latter calls it J. Jalapa, and the former says, ‘‘ that the true Purga de Xalapa 
delights only in a temperate climate, or rather an almost cold one, in shaded valleys, 
and on the slope of mountains.” The true plant has been fully described by Professor 
Don, in a paper read before the Linnean Society, from specimens grown from seeds 
sent by Dr. Schiede, which he procured from Chiconquiera, on the eastern declivity 
of the Mexican Andes, at an elevation of 6,000 feet. Mr. Don retains for this the 
name I. Jalapa, instead of Schiedeana and Purga, given it by Zuccarini and Wenderoth. 
The discovery of the true locality is important, as shewing that the Jalap requires 
a cool climate, and may no doubt therefore be cultivated in the Himalayas. 
129. HYDROLEACEZ. 
This small order, separated from Convolyulacee, contains genera which inhabit very 
different kinds of climate. Nama is found in both the East and West-Indies ; and 
N. (Hydrolea) zeylanica extends from the southern to the most northern parts of the 
plains of India, where it forms an ornament of damp and swampy situations. 
130. POLEMONIACEZ. 
This family, allied on one hand to Gentianex, and on the other to Convolvulacee, 
abounds chiefly in America, as in Chili, Peru, Mexico, and the more southern 
of the United States provinces, but especially in California. Dr. Richardson states 
54° as the most northern limit of the order. The genus Phlox has also a species in 
Siberia, and Polemorwwn extends from Europe across Siberia to Japan, and south- 
wards 
