64 STORAGE AND DIGESTION OF FOODS 



which are annuals that the food accumulated in one plant 

 is bequeathed in more or less permanent form to its off- 

 spring, being stored in seed. In the case of plants 

 which grow one season and seed the next, as do 

 beets, onions, etc., the food made during the first growing 

 season is stored in the roots and other underground parts, 

 and is used the following year in the production of flowers 

 and fruit. In the case of perennials the storage of food 

 may take place in the bark, in the roots, in the seeds and 

 fruits, in the pith, and in various other parts of the plant 

 body. Thus we find sugar stored in sugar beets and 

 onions. The sugar which is found in the sap of maples, 

 grape vines, and other perennials, comes from the digested 

 stores of starch deposited in various parts of the plant 

 body during the preceding season. Starch accumulates 

 in the tubers of the potato, underground, and is present 

 in corn and in the other grains. 



Starch may be conceived as a direct derivative of 

 sugar, obtained by withdrawing a molecule of water from 

 the molecule of sugar. Being insoluble it accumulates, 

 or is deposited, in special cells and in special organs of 

 the cell known as amyloplasts, and constitutes one of 

 the most compact and economical forms in which non- 

 nitrogenous food is accumulated and stored. 



Other Stored Foods. — In the tubers of the dahlia 

 the carbohydrate food accumulates in soluble form, but 

 not as sugar, remaining in solution in the form of inulin, 

 a substance of the same proportional composition as 

 starch and cellulose. It may be precipitated by dropping 

 pieces of dahlia tuber into strong alcohol or strong glyc- 

 erine, in which case it will come down in the form of 

 sphaero-crystals. In ivory-palm nuts, from which the 

 buttons of men's clothes are very commonly made, the 

 carbohydrate food of the plant is stored in the form of 

 cellulose which is applied to the cell-walls until they 

 become enormously thick; at the same time the cellulose 

 is so compact and firm that it is very hard. In various 



