the bottom off a narrow-necked bottle by pressing a red-hot poker or iron rod against it and leading the crack around the bottle. Invert a test-tube over the stem of the funnel. In sunlight bubbles of oxygen will arise and collect in the test-tube. If a sufficient quantity of oxygen has collected, a lighted taper inserted in the tube will glow with a brighter flame, showing the presence of oxygen in greater quantity than in the air. Shade the vessel. Are bubbles given off? For many reasons it is impracticable to continue this experiment longer than a few hours. =90.= A simpler experiment may be made if one of the waterweeds Cabomba (water-lily family) is available. Tie a number of branches together so that the basal ends shall make a small bundle. Place these in a large vessel of spring water, and insert a test-tube of water as before over the bundle. The bubbles will arise from the cut surfaces. Observe the bubbles on pond scum and waterweeds on a bright day. _To illustrate the results of respiration_ (CO_{2}). [Illustration: FIG. 122.—TO SHOW THE ESCAPE OF OXYGEN.] [Illustration: FIG. 123.—TO ILLUSTRATE A PRODUCT OF RESPIRATION.] [Illustration: FIG. 124.—RESPIRATION OF THICK ROOTS.] [Illustration: FIG. 125.—TO ILLUSTRATE TRANSPIRATION.] =91.= In a jar of germinating seeds (Fig. 123) place carefully a small dish of limewater and cover tightly. Put a similar dish in another jar of about the same air space. After a few hours compare the cloudiness or precipitate in the two vessels of limewater. =92.= Or, place a growing plant in a deep covered jar away from the light, and after a few hours insert a lighted candle or splinter. =93.= Or, perform a similar experiment with fresh roots of beets or turnips (Fig. 124) from which the leaves are mostly removed. In this case, the jar need not be kept dark; why? _To test transpiration._ =94.= Cut a succulent shoot of any plant, thrust the end of it through a hole in a cork, and stand it in a small bottle of water. Invert over this a fruit jar, and observe that a mist soon accumulates on the inside of the glass. In time drops of water form. =95.= The experiment may be varied as shown in Fig. 125. =96.= Or, invert the fruit jar over an entire plant, as shown in Fig. 126, taking care to cover the soil with oiled paper or rubber cloth to prevent evaporation from the soil. =97.= The test may also be made by placing the pot, properly protected, on balances, and the loss of weight will be noticed (Fig. 127). [Illustration: FIG. 126.—TO ILLUSTRATE TRANSPIRATION.] [Illustration: FIG. 127.—LOSS OF WATER.] [Illustration: FIG. 128.—TO SHOW SAP PRESSURE.]