THE CARBOHYDRATES PRODUCED IN CROPS 123 



for the production of starch much will, of course, depend 

 upon the particular circumstances, but a ton of maize per 

 acre will be a fairly good crop, and will barely produce half 

 a ton of starch. This might be compared with about seven 

 tons of potatoes per acre, producing rather over a ton of 

 starch. The cultivation of potatoes, to yield good crops, is, 

 however, expensive, in comparison with most of the cereals. 

 Potatoes, if kept cool, can be stored quite satisfactorily. 

 The large amount of water they contain is an objection for 

 transport purposes in comparison with the cereals* 



Sago. — The sago palm grows in tropical countries, best 

 on boggy soils, which are rich in humus. The palms are 

 cut down when the trunks have attained a height of about 

 twenty feet, the sap is allowed to drain, and the trunks, 

 sawn into lengths, split open, and the pith removed. The 

 pith consists of starch, mixed with fibrous materials, wliich 

 is then pounded in mortars, agitated with water, and the 

 starch separated as usual. The sago flour so obtain^ivc' 

 imported into this country, and is used for the mant 

 of glucose, and in the textile industries. The gramilj 

 sago which is made for the purpose of food is pijaj 

 from sago flour by mixing it with water into a veryCSti 

 paste, and gelatinizing by heat. " Granulated sago " is, 

 however, sometimes made from starches of other origin 

 than sago. 



Cassava and Tapioca. — The tuberous roots of the 

 shrub-like plants called sweet cassava and bitter cassava 

 are cultivated in the tropics for edible purposes. Cassava 

 flour only contains 2 pei cent, albuminoids. Owing to the 

 low demands of cassava for mineral matter, the crop is very 

 well suited for poor, sandy soils, but it requires a good supply 

 of air and water. The cultivation is as that of potatoes 

 and similar manuring gives increased crops. The yield is 

 about 5 tons per acre, producing i ton of starch and a little 

 cane sugar. Tapioca is made from cassava starch by stirring 

 the damp starch on hot iron plates. Cassava root contains 

 a cyanogenetic glucoside, which develops prussic acid in 

 the same manner as linseed (see p. 137). As in the case 



