aUM OF ECONOMIC PLANTS. 203 



a great depth, from the apex of which are produced broad leaves 

 (fronds), which float on the surface of the water iu such density as 

 to impede the navigation of vessels. It abounds in the meridian 

 of 40° west, and between the latitudes of 20° and 45° north, 

 covering the surface of the ocean for 1,000,000 square miles, 

 known as the Sargasso Sea. 



Gum, a general name for sticky matters exuding naturally 

 or by artificial wounds from many different kinds of trees, shrubs, 

 and herbs, of which the following are a few of the principal. 

 They consist of two kinds, those that dissolve in water and have 

 no smell, and those that contain a resin termed Gum-resin, and 

 burn with an aromatic odour, and dissolve in alcohol or other 

 solvents. 



Gum Acaroides. (See Grass Gum Trees.) 



Gum Alk, a gum -resin yielded by Pistada Terehinthus, a 

 small tree of the Cashew I^Tut family (Anacardiacese), native of 

 North Africa. 



Gum Anime. {See Gum Copal.) 



Gum Arabic. — This is obtained from several species ot Acacia, 

 a genus of the Bean family (Leguminosge). The principal gum- 

 yielding species are A, Seyal, A, arabica. A, nilotica. A, Senegal, 

 and A. Stenocarpa ; with a few exceptions, they are small spiny 

 trees, the first threebeing found widely dispersed in India, Western 

 Asia, and Central Africa, and the latter in Western Africa. The 

 gum exudes from the trees naturally, or is accelerated by making 

 incisions in the stems and branches ; it soon hardens, and is then 

 collected. It begins to flow at the commencement of the dry 

 season, which is generally about November. About the middle 

 of December the Moors encamp on the border of the Acacia forest, 

 and the harvest lasts six weeks, during which time the Moors 

 live almost entirely upon the gum. It is highly nutritious ; 

 six ounces of gum are sufficient to support a man for twenty- 

 four hours. It may be stated that Gum Arabic is collected in 

 localities throughout the whole of Africa, and is conveyed in 

 skins or bags of leather on camels to the ports of the Atlantic, 

 Mediterranean, and the Eed Sea, for shipment to various coun- 



