. A companion to Blackie's tropical readers, books I and II : containing suggestions for experiemnts and practical work . de, forming Starch. 1. Assimilation.— Picka green leaf in the after-noon of a day that hasbeen sunny, and test Starch will befound. 2. Assimilation will nottake place- in the Dark.—Put a pot plant in a darkcupboard for twenty-fourhours. Test with iodine;no starch will be found. 3. If Stomata are closed, no Assimilation will take place.—In the morning vaseline both sides of a leaf; pick itin the afternoon; test with iodine, and observe that nostarch will be foun
. A companion to Blackie's tropical readers, books I and II : containing suggestions for experiemnts and practical work . de, forming Starch. 1. Assimilation.— Picka green leaf in the after-noon of a day that hasbeen sunny, and test Starch will befound. 2. Assimilation will nottake place- in the Dark.—Put a pot plant in a darkcupboard for twenty-fourhours. Test with iodine;no starch will be found. 3. If Stomata are closed, no Assimilation will take place.—In the morning vaseline both sides of a leaf; pick itin the afternoon; test with iodine, and observe that nostarch will be found. (d) Plants give off Oxygen from the Carbon Dioxide takenin.—Put some watercress or duckweed in a vessel of ^Iodine Test for Starch in Leaves.—After the leaf has been picked, it shouldbe put in boiling water for two or three minutes. It should then be bleachedby soaking in alcohol. Put the leaf, when more or less colourless, in a solu-tion of iodine, prepared by dissolving a few crystals of iodine in alcohol or ina solution of potassium iodide. If starch is present the leaf will be coloureddark Fig. 25.—Plant giving off Oxygen EXPERIMENTS AND PRACTICAL WORK 57 water; place it in the sunshine, and notice the rise ofbubbles of oxygen. This gas may be collected by put-ting a funnel over the leaves and inserting a test tubewith water (see fig. 25). Test for oxygen by carefullyremoving the test tube and inserting a glowing taper. Expt. 80. Plants take in Oxygen and give out Car-bon Dioxide.—Put some growing shoots in a bottle con-taining a little water; cork tightly and put in the about twenty-four hours test with lime-water andobserve the precipitate due to the carbon dioxide givenout by the young shoots. HOW PLANTS ARE REARED—I and II (See Tropical Readers, Book II, pp. 74-79.) Expt. 81. Necessity for Selection of Seed.—Selectseeds from the best fruit of four trees that have beennoticed to bear well. Plant in a suitable position andwell-prepa
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