THE STOEAGE OF EESEEVE MATEEIALS 239 



mentioned, in solution in the cell-sap, but it can readily be 

 made to crystallise out or to be precipitated in an amor- 

 phous condition by the application of alcohol (fig. 113). 



We find many instances of the occurrence of various 

 sugars as reserve materials. Cane-sugar is present in large 

 quantities in the succulent parenchyma of the roots of the 

 Beet and the Mangel-wurzel, and of the stems of the Sugar- 

 cane ; grape-sugar is found in the leaves of the bulbs of 

 the Onion and allied plants ; small quantities of raffinose 

 are met with in the grains of barley and other cereals. 



FIG. 113. SPH.EBO-CKYSTALS OF INTJLIN FROM THE ARTICHOKE. 



small crystals in the interior of cells treated with alcohol; B, large crystals 

 extending through many cells. 



These are all present in solution in the cell-sap, as has 

 previously been mentioned. 



In many cases carbohydrate reserve materials are found 

 to take the form of considerable thickening of the cell- 

 walls. That these are really deposited in seeds with a 

 view to subsequent utilisation is evident from a study of 

 the endosperm of many palms, the cells of which consist of 

 little else ; the walls are so thick that the cavities are 

 almost obliterated, and the small space that is left between 

 the thickened walls contains apparently nothing but a 

 small amount of protoplasm with which some amorphous 

 protein matter is mixed. Even the unthickened cell-walls 

 of most seeds must be looked upon as reserve food material, 



