312 INTRODUCTION TO BOTANY 



About one third of the world's supply of sugar comes from 

 the sugar cane (Saccharum officinarwn), which has at least a 

 dozen varieties that thrive in tropical and sub-tropical coun- 

 tries (fig. 234). This plant has a very heavy root system, 

 from which several stalks grow. Its leaves are large and 

 numerous, so that much chlorophyll work is possible ; hence 

 much sugar may be made by the plant. The stalks when full- 

 grown are so well filled with sugar-laden sap that natives 

 often use them directly as food. The sap from good cane may 

 contain from 17 to 18 per cent of sugar. After the leaves are 

 stripped off, the stalks are cut and the sap is pressed from 

 them by means of machinery specially designed for that pur- 

 pose; after this the water is removed from the sugar by 

 evaporation. Some sugar cane is grown in this country, but 

 sorghum is more widely distributed and produces a sirup that 

 is extensively used. 1 



Sugar beets (Beta vulgaris) have been grown in Europe for 

 many generations, but it is only in recent years that they have 

 been widely grown in the United States. They have already 

 become a prominent factor in the sugar industry. Sugar beets 

 thrive in temperate climates, mature in a relatively short sea- 

 son, and grow well in a wide range of soil conditions. Besides 

 these advantages, they are very productive. The sugar pro- 

 duced from beets is rapidly coming into general favor. 2 



295. Fiber plants. Primitive people learned to use the 

 strong-fibered grasses and the tough bark of some trees in mak- 

 ing bands and cords for tying various articles. Leatherwood, 

 or moosewood (JDirca palustris), and Indian hemp (Apocynum 

 cannabinum), often so used by the early settlers in this country, 

 have fibers of very great strength, which, when dry, are almost 

 as strong as leather thongs. The making of cordage from plant 

 fibers has become an important industry. Many grasses, palms, 

 hemps, etc. have extremely long, strong fibrovascular bundles, 

 which, when removed and twisted together, make twines of 



1 " Sugar Cane in Porto Rico," Bulletin 9, Porto Rico Agr. Exp. Sta., 1910. 



2 ft The Sugar Beet," Farmers' Bulletin 52, U.S. Dept. Agr., 1910. 



