II.] ORGANIC MATTER OF PLANTS. 19 



the name which distinguishes them. It may be well 

 at this stage to notice very briefly the several bodies 

 we have thus divided into two classes. 



33. Starch is a white granular body very abundant 

 in vegetation, especially in corn and some " root" crops. 

 If you place a little wheat flour in a fine gauze bag, 

 and wash it in a glass, the water quickly assumes a 

 milky appearance. In a short time a white deposit is 

 formed in the glass, and the water has again become 

 bright and clear. The sediment thus obtained is 

 starch, which has been separated from the wheat 

 flour. If the bag were now opened, a glutinous mass 

 would be found, in appearance something like soft 

 threads of india rubber. This is the gluten of wheat, 

 to which we shall have to refer subsequently. Gum 

 exists in plants generally in a liquid condition, but we 

 occasionally find it thrown out on the surface in a 

 more or less hardened and transparent form, especially 

 in the case of fruit trees, when the bark has been 

 injured. Sugar is also found in vegetation in a 

 liquid form. In the well known sugar-cane, sugar- 

 beet, and sugar-maple, it is found in great abundance, 

 and from all of these sugar is obtained for the public 

 supply. You should however remember that it is 

 present in our cultivated plants even when not in 

 sufficient quantity for it to be separated for use. It 

 has many important duties devolving upon it in pro- 

 moting the growth of the plant, and its passage through 

 the plant, mingled with the sap, enables it to perform 

 these duties. Cellulose is so called because it is the 

 matter of which the cells of plants are constructed, 

 and it is sometimes known as cellular matter. It 

 varies very much in its firmness and strength. When 

 first it is produced in the plant, it is excessively tender 

 and fragile, but as it becomes strengthened by growth 

 . so it gradually becomes more rigid and tough, and at 

 length assumes the form of woody fibre. These 

 bodies are very similar in composition, and are capable 



