PROTOPLASM AND PLANT-CELLS. 13 



Practical Studies. — {a) Mount in water several thin longitudinal 

 sections of the stem of the Spiderwort (Tradescantia) and note the 

 bundles of needle shaped crystals in enlarged, thin-walled cells. 

 Many crystals will be found floating free in the water, having been 

 sepai-ated in the preparation of the specimen. 



(6) Similar sections of the stem of the Evening Primrose, Fuchsia, 

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

 show needle-shaped crystals. 



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

 scales), Pigweed or Lamb's Qnai'ters (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,,H,,0„), and glucose, or grape-sugar (0„H,,0,J, which 

 differ in their sweetness as well as in other properties. 



31. Cane-sugar exists in great abundance in the cell-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 iigs it is 

 the only sugar present, while in apricots, peaches, pine- 

 apples, plums, and strawberries it is mixed with cane-sugar. 



32. Inulin (Cj,Hj,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- 



