Laboratory and field manual of botany . or a few minutes, to killthe protoplasmic contents of the cells and to soften and swellthe starch grains. Soak the leaves, after boiling, in strong, hotalcohol for half an hour, to dissolve out the chlorophyll, which 1 FJodea, yfyriophylliDn, (hriisnspjciimm, Potainogeton, any of the preenaquatic tlowcriu; plants, the a(niatic moss, Fontinalis, or even the common pondscum, Spiroffyra, will (h) for this experiment. 2 Some of the earlier bnhhles may contain a good deal of air which wasdissolved in the water and set free as it grows warm, but the later bubb
Laboratory and field manual of botany . or a few minutes, to killthe protoplasmic contents of the cells and to soften and swellthe starch grains. Soak the leaves, after boiling, in strong, hotalcohol for half an hour, to dissolve out the chlorophyll, which 1 FJodea, yfyriophylliDn, (hriisnspjciimm, Potainogeton, any of the preenaquatic tlowcriu; plants, the a(niatic moss, Fontinalis, or even the common pondscum, Spiroffyra, will (h) for this experiment. 2 Some of the earlier bnhhles may contain a good deal of air which wasdissolved in the water and set free as it grows warm, but the later bubbles willbe fairly pure oxygen. 58 STKUCTUJIE AND JIIYSlOLO(;V OF SEED PLANTS might obscure the starch test. Heat the alcohol in a water bathaway from any flame. Place the leaves for ten or fifteen minutesin a solution of iodine, rinse off with water, put in a white plateor saucer, and note what portions of the leaf, if any, show thepresence of starch. References. Detmer-Moor, 9 ; Ganong, 10;. Darwin andActon, 11 ; Pfeffer-Ewart, 31, EXPERIMENT XXXTTI Consumption of starch in nasturtium (Tropaeolum) leaves.* * Select some healthy leaves of Trojxvoluni on a plant growingvigorously indoors, or, still better, in the open air. Shut off the sunlight from parts of the selectedleaves (which are to be left on theplant and as little injured as possible)by pinning circular disks of corkloosely on opposite sides of the leaf,as shown in Fig. 3. On the afternoonof the next day remove from the plantthese leaves and (for control purposes)some others to which no cork diskswere attached. Treat all as describedin the preceding experiment, takingespecial pains to get rid of the chlorophyll by changing thealcohol as many times as may be necessary. AVhat does thisexperiment show in regard to the consumption of starch in theleaf ? What has caused its disappearance ? ^ It may be fairly taken for granted that if the leaf contained anystarch when the corks were pinned onto it, all parts of it wereso
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