218 PLANTS AND MAN 



cuttings taken from the upper regions of old stems, and planted 

 in level, deeply plowed fields, where they sprout in about two 

 weeks. For the first few months, until the young canes are well 

 established, constant care in weeding, cultivation, and frequent 

 fertilization is necessary; later demands on the part of the plant 

 are mainly for water and heat, which is abundantly supplied by 

 tropical precipitation and sunshine. From ten to twenty months 

 of growth, depending upon location and climate, is necessary to 

 mature the cane crop to the desired sugar content. This is 

 closely watched so that the cane may be cut at exactly the right 

 time, usually found to be when the flowers of the cane are just 

 past their prime. A delay beyond this time would give a de- 

 creased yield since sugar, stored temporarily in the stem, is 

 transported to the developing seed where it is changed into 

 starches and fats. The stems are cut close to the ground with a 

 heavy knife and the underground parts left to sprout again, giving 

 two or three more crops before replanting is necessary. Sugar cane 

 culture in southern Louisiana, Texas and Florida is only moder- 

 ately successful, since there is seldom the required length of a 

 frost-free growing season to properly mature the cane. Frost is 

 ruinous to cane, causing formation of undesirable by-products in 

 the plant tissues. 



Large central mills for grinding and extracting the sugar cane 

 have now replaced many of the small, primitive, individually 

 owned mills formerly found in sugar producing regions. Here the 

 cane is crushed and rolled between heavy sets of rollers until it is 

 practically dry and devoid of its sugar-containing juices; this 

 residue is used as a fuel in the boilers of the mill, or as a raw 

 material for the manufacture of paper and wall boards. The 

 juice contains sucrose and other sugars, as well as numerous 

 impurities. The latter are removed by a series of purifying pro- 

 cesses involving straining or filtering to remove solid particles, 

 heating with the addition of sulfur to precipitate protein sub- 

 stances, and of lime to neutralize acids and to precipitate other 

 soluble substances, and finally the removal by filters of all precipi- 

 tated substances. The filtered juice — clear, dark colored and 

 containing only sugars and closely related carbohydrates — is now 

 ready for concentration. This is brought about by boiling the 

 juice in great open kettles or vacuum pans until the desired 



