12 RESPIRATION. [CH. I 



treated in the same way to answer well. Gather a large 

 handful of dandelion flowers 1 , cutting the stalks just below 

 the head, place them in a large funnel supported in a 

 beaker half filled with KHO. Hang a thermometer so 

 that the bulb is covered by the flowers, and let the control 

 thermometer be supported in a funnel containing coarse 

 sawdust slightly moistened and loosely packed. This ar- 

 rangement is meant to equalise the conditions of the two 

 thermometers, and to prevent the thermometer 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 2 . 



(10) Oxygen necessary. 



Several of the earlier observers have shown that 

 when the air is replaced by indifferent gas the tempera- 

 ture falls. Pfeffer 3 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 



1 Or in winter of young flowers and buds of a small-flowered Chrysan- 

 themum. 



~ To demonstrate the heat of respiration, Professor Errera of Brussels 

 (as he is good enough to inform us) uses a Leslie's Differential Thermo- 

 meter. One of the air-bulbs is plunged in a funnel filled with germinating 

 barley and covered loosely with damp paper. The other bulb is in a 

 similar funnel containing killed barley. 



3 See Pfeffer, Physiologie, n. p. 403. Fig. 40. 



