18 BOTANY. 



Balsam or Toucb-me-not (Impatiens), and Garden Rhubarb will also 

 show needle-sbaped crystals. 



(c) Other crystal forms may be obtained from the beet, onion (the 

 scales), Pigweed, or Lamb's-quarters (Chenopodium), etc. 



29. The Cell-sap. — All parts of a living cell are satura- 

 ted with water. It enters into the structure of the cell- 

 wall; it makes up the greater part of the bulk of the pro- 

 toplasm, and it fills the vacuoles. It holds in solution the 

 food-materials absorbed from the air and soil, and the sur- 

 plus soluble substances manufactured by the plant. 



30. Among the many substances dissolved in the cell- 

 sap the more important are Sugar and Inulin. Of the 

 former there are two varieties, viz. , sucrose, or cane-sugar 

 (C,jH„Oj,), and glucose, or grape-sugar (CgHijOJ, which 

 differ in their sweetness as well as in other properties. 



31. Cane-sugar exists in great abundance in the ceU-sap 

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

 in greater or less quantity in nearly all higher plants. 

 Grape-sugar is found in many fruits, sometimes 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. 



32. Inulin (C,H,„OJ is a soluble substance related to 

 starch and sugar, which is found mainly in the cell-sap of 

 certain Composites, as the sunflower, dahlia, elecampane 

 (Inula), etc. 



Practical Studies.— (a) Make a thin section of the stem of any 

 herbaceous plant, as a Geranium ; examine at once without a cover- 

 glass, noting the wateriness. Lay the specimen aside for half an 

 hour or so, and then note its shrinkage by loss of water. 



(6) Mount a few plants of Pond Scum (Spirogyra) in a very little 

 water. Examine under the high power of the microscope, and while 

 doing this flow glycerineunder the cover-glass. The. glycerine im- 



