. Foundations of Botany. Botany. 170 FOUNDATIONS OF BOTANY EXPERIMENT XXXY Occurrence of Starch in Nasturtium Leaves. — Toward the close of a very sunny day collect some bean leaves or leaves of nasturtium (Tropceolum). Boil these in water for a few minutes, to kill the protoplasmic contents of the cells and to soften and swell the starch Soak the leaves, after boiling, in strong alcohol for a day or two, to dissolve out the chlorophyll, which would otherwise make it diffi- cult to see the blue color of the starch test, if any were obtained. Rinse out the alcohol with plenty of water
. Foundations of Botany. Botany. 170 FOUNDATIONS OF BOTANY EXPERIMENT XXXY Occurrence of Starch in Nasturtium Leaves. — Toward the close of a very sunny day collect some bean leaves or leaves of nasturtium (Tropceolum). Boil these in water for a few minutes, to kill the protoplasmic contents of the cells and to soften and swell the starch Soak the leaves, after boiling, in strong alcohol for a day or two, to dissolve out the chlorophyll, which would otherwise make it diffi- cult to see the blue color of the starch test, if any were obtained. Rinse out the alcohol with plenty of water and then place the leaves for ten or fifteen minutes in a solution of iodine, rinse off with water and note what portions of the leaf, if any, show the presence of starch. EXPERIMENT XXXVI Consumption of Starch in Nasturtium (Tropceolum) Leaves.—Select some healthy leaves of Tropseolum on a plant growing vigorously indoors or, still better, in the open air. Shut off the sunlight from parts of the selected leaves (which are to be left on the plant and as little injured as may be) by pinning circular disks of cork on opposite sides of the leaf, as shown in Fig. 123. On the afternoon of the next day remove these leaves from the plant and treat as described in the preceding experiment, taking especial pains to get rid of all the chlorophyll by changing the alcohol as many times as may be neces- sary. What does this experiment show in regard to the consump- tion of starch in the leaf? What has caused its disappearance? 182. Rate at which Starch is manufactured. — The amount of starch made in a day by any given area of 1 The leaves, collected as above described, may, after boiling, be kept in alcohol for winter use. They also make excellent material for the micro- scopical study of starch in the Fig. 123.—Leaf of Tropseo- lum partly covered with Disks of Cork and ex- posed to Please note that these images are extracted from scanned page images that may have
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