TUBIFLORAE — CONVOLVULACEAE 



699 



Batatas), which has been widely cultivated in all tropical and sub-tropical coun- 

 tries and is a well known and cultivated plant in the United States. There 

 are many varieties. In the South the large varieties are called yams, but these 

 should not be confused with the Chinese yam (Dioscorea), which forms an im- 

 portant article of food in tropical countries, in the islands of the Pacific and 

 in New Zealand. The man of the earth {Ipomoea fastigiata) was used by the 

 Indians as food. It has properties similar to Jalap, for which it is sometimes 

 substituted. The Ipomoea Jalapa, native to Mexico, produces a large root 

 which is also a purgative and contains a glucoside convohulin Cg^H.^O^^. 

 Several plants of the order, like the moon-flower (Ipomoea Bona-nox), the 

 morning-glory (Ipomoea purpurea) and cypress vine (Ipomoea Quamoclit) are 

 cultivated for ornamental purposes. Several, like Jalap (Ipomoea Purga) and 

 (/. congesta) are used in medicine and are strong purgatives. The scammony 

 (Convolvulus Scamtnonia) of Western Asia is also used as a purgative, the 

 milkv juice being collected when hard, it contains scammonin C,,H^„0,„. 

 Convolvulus scoparius and C. floridus, furnishing the oil of rhodium, are small 

 shrubby species of the Canary Islands. The wood is strongly scented and the 

 oil is used to adulterate attar of roses. 



Fig. 401. Sweet Potato (Ipomoea 

 Batatas). A well known cultivated 

 plant in tropical and sub-tropical 

 countries. (From Vesque's Traite 

 de Botanique.) 



