IN EXTRA -TROPICAL COUNTRIES. 157 



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. Orizabensis, Ledanois, also yields jalap, 

 according to Hanbury. 



Ipomcea simulans, Hanbury. 



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

 Sierra Gorda jalap, is derived. I. operculata, Mart., yields 

 the Brazilian jalap. 



Iris Florentina, Linne. 



Countries around the Mediterranean Sea. The well-known 

 Orris root is obtained from this species. Of the same geo- 

 graphic 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 perhaps produce dye with equal advantage. 

 Bossier enumerates merely as Oriental twenty-eight kinds. 



Isonandra Gutta, Hooker.* (Didropsis Gutta } Benth.) 



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

 sula. It seems not altogether hopeless to render this highly 

 important tree a denizen of the mildest wood regions, in tem- 

 perate 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 exsicca- 

 tion, otherwise the percha becomes brittle; 5 to 20 catties 

 yielded by one tree. 



Jacaranda mimosifolia, Don. 



Brazil. This tree, with /. Brazilian* and /. oUusifolia 



