FATS AND FIXED OILS 163 



e. Inulin is a carbohydrate possessing the same percentage 

 composition as starch ; it is soluble in water, and is met with dis- 

 solved in the cell-sap of many plants belonging to the Compositae, 

 Campanulaceae and other orders. It is also found in the bulbs 

 of many plants belonging to the Liliaceae and Amaryllidacese, as 

 well as in the leaves and other vegetative parts of these plants. 



Inulin is especially abundant in dahlia and chicory roots, and 

 in tubers of Jerusalem artichoke, where it takes the place of starch 

 as a reserve-food. When portions of these roots and tubers are 

 placed in dilute alcohol for several days, the inulin separates in 

 the form of solid spherical masses of needle-like crystals, arranged 

 in a characteristic radiated manner (sphaerites). 



Inulin does "not reduce Fehling's solution, but when boiled for 

 a long time with water, or for a short time with dilute acids, it is 

 converted completely into levulose. 



Ex. 90. — Soak a piece of a dahlia root in strong methylated spirit for several 

 weeks : cut sections and mount in pure glycerine. Examine and draw the 

 sphaerocrystals of inulin. 



2. Fats and fixed oils. — These substances, which are mixtures 

 of different compounds of glycerine and fatty acids, contain the 

 same three elements as the carbohydrates, but possess less oxygen 

 proportionately to hydrogen than the latter substances. They 

 are at first most frequently observed in the form of small round 

 drops of irregular softish semi-solid particles within the cytoplasm 

 of cells : afterwards the drops run together and are then excreted 

 into the cell-sap where they accumulate. 



Oils and fats are reserve plant-foods, and are consequently 

 most abundant in the endosperm and cotyledons of seeds, and 

 in certain fruits. The seeds of the rape plant contain on an 

 average 42 per cent. ; flax-seeds (linseed), 36 per cent., and cotton 

 seeds, 25 per cent, of oil. 



The various kinds of ' Oil-cakes ' used for feeding cattle are 

 formed from the residue of different seeds and fruits, the greater 



