192 



STORAGE OF FOOD AND WATER 



apart so that they are not themselves destroyed in the process. 

 The result of this is that a small amount of enzyme can digest 

 a relatively very large quantity of food, even up to 100,000 or 

 more times its own volume. 



Some of the many kinds of ferments produced by plants 

 have been classified and named. Thus diastase converts starch 

 into maltose (malt sugar). Maltase converts maltose into glu- 

 cose (grape sugar). Inulase converts inulin iqto fructose (fruit 

 sugar). Inveriase splits saccharose (cane sugar) into glucose 

 and fructose. Cytase changes cellulose to glucose. Pectase 

 changes pectic substances in the cell-wall to vegetable jelly. 

 Emulsin and myrosin are representative of enzymes acting 

 on glucosides and breaking them up into glucose and other 

 substances. 



A group of enzymes known as lipases or steapsins split up 

 fats and oils into fatty acids and glycerine. The enzymes, 



called proteolytic enzymes, 

 that digest proteids are 

 similar to the pepsins and 

 trypsins pf the; stomach and 

 pancreas of animals. The 

 pepsins change proteids to 

 the soluble peptones, and 

 trypsins convert peptones' 

 or proteids directly into 

 amido-acids. The trypsins 

 are the more compioE^ of 

 the proteolytic .en^yme^ in 

 plants. '^ 



These enzymes occur in every cell where the food that they 

 are fitted to digest is stored even transiently. In fact, dias- 

 tatic, inverting, and tryptic enzymes are so common that they 

 seem to be a part of every protoplast. There are, however, 

 in special cases, cells or groups of cells devoted to the secretion 

 of enzymes, as in the root of the horse-radish; and in the whole 

 family of grasses the epidermis of the cotyledon secretes enzymes 



Fig. 104. — Enzyme-secreting cells of date 

 cotyledon at A; and of cotyledon of Indian 

 com at B. The secreting cells are at e. 



