8 OILY SEEDS. [CH. I 



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 readings of the two thermometers should 

 now become practically equal, and it should be possible 

 to re-establish the difference by readmitting air. 



(10) Oermmation 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, Physiologie, ii. p. 403. Fig. 40. 



