166 SELECT PLANTS FOR INDUSTRIAL CULTURE 



Ipomoea paniculata, B. Brown. 



Almost a cosmopolitan plant on tropical coasts ; thus indigenous to 

 North Australia and the warmer parts of East Australia. The 

 tubers of this species also are edible. If hardy, the plant would 

 deserve cultivation. 



Ipomoea purga, Wenderoth. 



Mountains of Mexico. The true Jalap. This species yields the 

 medicinal jalap root. It has recently been cultivated with apparent 

 success even at New York ; thus it is entitled to a trial in warm 

 woodlands. Active principle ; the resinous convolvulin. I. Oriza- 

 bensis, Ledanois, also yields jalap, according to Hanbury. 



Ipomoea simulans, Hanbury. 



Mexico. From this species the Tampico jalap, or rather the Sierra 

 Gorda jalap, is derived. I. operculata, Mart., yield the Brazilian 

 jalap. 



Iris Florentina, Linne. 



Countries around the Mediterranean Sea. The well-known Orris 

 root is obtained from this species. Of the same geographic range 

 is Iris juncea, Poizet, the edible root of which is known by the 

 name of Zeloak among the Algerian natives (Simmons). 



Isatis indigotica, Fortune. 



North China. Perennial, almost shrubby. The use is similar to 

 that of the following plant. 



Isatis tinctoria, Linne. 



Dyer's Woad. From the Mediterranean regions through part of 

 the Orient, apparently extending as far as Japan. A tall herb of 

 two years' duration. The blue dye is obtained from the fermented 

 leaves. Woad succeeds best in rich limestone ground. Contains 

 luteolin. Many other species of Isatis, mostly Asiatic, may per- 

 haps produce dye with equal advantage. Bossier enumerates 

 merely as Oriental twenty-eight kinds. 



Isonandra Gutta, Hooker.* (Dickopsis Gutta, Benth.) 



The Gutta-percha Tree or the Gutta Taban. Malayan Peninsula. 

 It seems not altogether hopeless to render this highly important 

 tree a denizen of the mildest wood regions, in temperate climes, 

 Murton having traced it to elevations of 3,500 feet. The milky 

 sap, obtained by ringing the bark at 5 to 15 inches interstices, is 

 boiled for an hour before gradual exsiccation, otherwise the percha 

 becomes brittle ; 5 to 20 catties yielded by one tree. 



