CH. l] RISE OF TEMPERATURE. 7 



(7) Rise of Temperature. 



The spadix of an Arum is the classical material for 

 demonstrating the heat produced by respiration in plants. 

 We have used the British Arum maculatum, but for some 

 reason the experiment has not always succeeded. Remove 

 the spathe from 4 or 5 spadices (of which the spathes 

 are just beginning to expand) and fix their stalks in wet 

 sand, so that the specimens stand vertically in a ring. 

 Suspend a delicate thermometer in such a way that 

 the bulb falls among the Arums, and wrap them round 

 with a flock of cotton wool so that they may touch the 

 bulb. Kraus' has shown that the respiration of Arums 

 is easily affected by any injury to the surface of the 

 spadix, the specimens must therefore be delicately handled. 

 Hang a second thermometer (which must be previously 

 compared with the first) close to the Arums, and cover all 

 with a bell-jar standing in water. The bell-jar is necessary 

 to prevent currents of air. 



(8) Rise of temperature. 



The following is Sachs' arrangement for showing the 

 rise of temperature in germinating peas'. We have found 

 flowers, such as those of dandelions, treated in the same 

 way to answer well. Gather a large handful of dandelion 

 flowers^ 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 



' G. Kraus, Naturforsch. Ges. Halle, xvi. 1884. 



2 Sachs' Text-book, Ed. ii. p. 724. Fig. 472. 



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

 themum. 



