Practical physiology of plants / by Francis Darwin and E. Hamilton Acton.

  • Francis Darwin
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Practical physiology of plants / by Francis Darwin and E. Hamilton Acton. Source: Wellcome Collection.

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    covered by the flowers, and let the control thermometer be supported in a funnel containing coarse sawdust slightly moistened and loosely packed. This arrangement is meant to equalise the conditions of the two thermometers, and to prevent the bulb among the flowers acting as a wet- bulb. We find, with the control thermometer hanging simply in the air, that the flowers keep about 2° C. above the control temperature. As before, the whole must be covered with a bell-jar. Sachs uses a tubulated bell of which the opening is plugged with cotton-wool. (9) Oxygen necessary. Several of the earlier observers have shown that when the air is replaced by indifferent gas the tempera- ture falls. Pfeffer^ recommends that the germinating seeds or other material should be placed in a glass balloon having three apertures—one of which serves for a thermo- meter. When the temperature of the respiring material has been proved to be steadily above that of the surround- ing air, the atmosphere in the balloon is replaced by hydrogen, for which purpose the two lateral apertures will serve. The i-eadings of the two thermometers should now become practically equal, and it should be possible to re-establish the difference by readmitting aii-. (10) Germination of oily seeds. Repeat experiment 2, using oily seeds for the ger- minating material, and omitting the test-tube of KHO. Hemp seeds will serve the purpose: they should not be ' See Pfeffer, Physiologic, ii. p. 403. Fig. 40.
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