TRANSLOCATION AND STORAGE OF FOODS 223 



4. The surplus organic material manufactured by a plant is 

 transferred to various parts of its body to be stored for future 

 use. Among annuals the reserve-food is accumulated only in 

 the seeds ; in wheat and other cereals the endosperm of the 

 seed becomes gradually filled with it, while in peas, beans and 

 many annuals the reserve is stored in the cotyledons of the 

 embryo. 



Among biennials and perennials, the seeds are similarly stored 

 with reserve-food; but such plants,, before the end of one 

 growing-season, accumulate and store a considerable quantity of 

 organic material in their vegetative organs, which material serves 

 for the nutrition and growth of the cambium, buds and roots 

 during the earlier part of the succeeding season. 



In turnips, carrots and mangel the ressrve-material is stored 

 in the roots : in onions and tulips it is accumulated in the leaves 

 of the bulbs, in potatoes in the tubers, while in hops and many 

 herbaceous perennials it is hoarded in the rhizomes or rootstocks. 



Trees and shrubs store their reserve-material chiefly in the 

 parenchyma of the cortex and medullary rays in the stems. 



In the onion and many bulbs the carbohydrate reserve is 

 stored chiefly in the form of dextrose, while many fruits store 

 levulose also in their cell-sap. 



In the sugar-cane, sugar-beet, turnip and other roots the 

 reserve is cane-sugar dissolved in the cell-sap ; in the tubers of 

 the Jerusalem artichoke inulin takes the place of sugar. In 

 the majority of plants the reserve-materials are chiefly stored in 

 a solid insoluble form, in which state they take up less space than 

 they would do in solution. 



The commonest solid carbohydrate reserve-material is starch 

 which occurs in the form of small grains previously described 

 (p. 156). In some instances very minute particles of starch are 

 temporarily formed within the cytoplasm but the largei starch- 

 grains present in the special storage centres are produced by the 

 leucoplasts of the cells from sugars which are transferred to them 



