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 
separated 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 Quarters (Chenopodium), ete. 
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 (C,,H,,0,,), 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 figs it is 
the only sugar present, while in apricots, peaches, pinc- 
apples, plums, and strawberries it is mixed with cane-sugar. 
32. Inulin (C,,H,,O,,) 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), ete. 
Practical Studies.—(a) Make a thin section of the stem of any 
herbaceous plant, as a Geranium; examive at once without a cover- 
