63 BOTANY. 



§ V. The Cell Sap. 



81. — All parts of a living cell are saturated with water. It 

 enters into the structure of the cell-wall ; it makes up the 

 greater part of the bulk of the protoplasm, and it fills the 

 vacuoles. It holds in solution (not necessarily, however, in 

 equal proportions in all its parts) the food-materials absorbed 

 by the plant, and the surplus soluble products of assimila- 

 tion and metastasis. 



82 Among the more important substances dissolved in 



the cell sap are Sugar and luulm. Of the former there- 

 are two varieties, viz., sucrose, or cane sugar (C„ H^^ 0„), 

 and glucose (or laevulose), or fruit sugar (Cj, H^^ 0„), which 

 difEer in their sweetness, as well as in other properties. 



83. — Cane sugar exists in great abundance in the coll sap 

 of sugar cane, sugar maple, sugar beet, Indian corn, and in 

 greater or less quantity in nearly all higher plants. Fruit 

 sugar, as its name indicates, is found in many fruits, some- 

 times mixed with cane sugar ; thus in grapes, cherries,, 

 gooseberries, and figs it is the only sugar present, while in 

 apricots, peaches, pine-apples, plums, and strawberries it is. 

 mixed with cane sugar. 



84. — Inulin (C , H,„ 0,„) is a substance related to starch 

 and sugar, and found mainly in certain Compositse, e.g., 

 DaJilia, Heliantlius, Inula, Taraxacum, etc. It may b& 

 separated from the cell sap by alcohol, glycerine, and other 

 agents, and it then assumes the form of sphere-crystals. By 

 boiling in dilute hydrochloric or sulphuric acid inuline is. 

 transformed into glucose. 



§ VI. Oils, Kesins, Gums, Acids, and Alkaloids. 



85. — The fixed oils, as olive, castor, linseed, and palm oil, 

 are secreted in many plant-cells, particularly in the seeds. 

 They occur as separated drops among the other contents of 

 the cells. In some instances the tissiies contain from thirty- 

 five to forty per cent of oil. 



86. — The essential oils, the resins, and gums are mainly 

 the products of special cells in the plant. These secreting cells 



