68 HOW CROPS GROW. 



washed with water to which some alcohol has been added. ITennebcrg's 

 Journal fur LandicirtJischaft, 1863, p. 206. 



Iltulin, C ia H 20 O 10 , closely resembles starch in many 

 points, and appears to replace that body in the roots of 

 the artichoke, elecampane, dahlia, dandelion, chicory, and 

 other plants of the same natural family (compositor). It 

 may be obtained in the form of minute white grains, 

 which dissolve easily in hot water, and mostly separate 

 again as the water cools. Unlike starch, inulin exists in a 

 liquid form in the roots above named, and separates in 

 grains from the clear pressed juice when this is kept some 

 time. According to Bouchardat, the juice of the dahlia 

 tuber, expressed in winter, becomes a semi-solid white mass 

 in this way, after reposing some hours, from the separa- 

 tion of 8 per cent of this substance. 



Inulin, when pure, gives no coloration with iodine. It 

 may be recognized in plants, where it occurs in a solution 

 usually of the consistence of a thin oil, by soaking a slice 

 of the plant in strong alcohol. Inulin is insoluble in this 

 liquid, and under its influence shortly separates as a solid 

 in the form of spherical granules, which may be identified 

 with the aid of the microscope. 



When long boiled with water it is slowly but complete- 

 ly converted into a kind of sugar, (levulose) ; hot dilute 

 acids accomplish the same transformation in a short time. 

 It is digested by animals, and doubtless has the same value 

 for food as starch. 



In chemical composition, inulin agrees perfectly with 

 cellulose and starch ; see p. 60. 



Dextrin, C 12 IT 20 O 10 , has been thought to occur in small 

 quantity dissolved in the sap of all plants. According to 

 Yon Bibra's late investigations, the substance existing in 

 bread-grains which earlier experimenters believed to be 

 dextrin, is in reality gum. Busse, who has still more 

 recently examined various young cereal plants and seeds, 



