EXCRETION OF CARBON DIOXIDE 



253 



Injuries and wounds also tend to increase re- 

 spiration locally as shown by excretion of carbon 

 dioxide. 1 



Respiration is also influenced to a slight extent 

 by the pressure of the oxygen in the atmosphere. 

 Any decrease below the normal exercises a corre- 

 sponding effect on the excretion of carbon dioxide, 

 and stimulates intramolecular respiration, while an 

 increase above the normal accelerates the process 

 but slightly and is injurious to the organism. An 

 accumulation of the products of respiration retards 

 the process. 



The evolution of heat is exhibited in a marked 

 degree by unfolding flowers, germinating seeds and 

 growing sporophores of fleshy fungi, and a tempera- 

 ture of many degrees above that of the surrounding 

 air may be reached. Phosphorescence as a result 

 of respiration is exhibited by a few special forms of 

 fungi. 



320. Demonstration of Excretion of Carbon Dioxide 

 During Aerobic Respiration. Place a few dozen 

 seeds in a germinator until the roots are a centi- 

 meter long and then put into a glass cylinder of a 

 capacity of about a liter. Close the jar with a 

 ground-glass plate or stopper and keep at room 

 temperature. A day later cautiously push the 

 ground-glass to one side and thrust in the jar a 

 short piece of burning candle fastened to the end 

 of a wire. It will be truickly extinguished, de- 

 noting the absence of oxygen. Close the jar 

 and prepare a fresh solution of barium hydrate 

 in a closed test-tube. Secure two wide -mouthed 



1 Zaleski, W. Zur Aetherwirkung auf die Stoffumwandlung 

 in den Pflanzen. Ber. Deut. Bot. Ges. 18 : 292. 1900. 



Richards, H. M. Respiration of wounded plants. Annals 

 of Botany, 10 : 531. 1896. 



Fig. 126. Dem- 

 onstration of the 

 excretion of car- 

 bon dioxide in 

 germinating seeds. 

 A, mercury, which 

 is seen to have 

 risen in the tube at 

 the close of an ex- 

 periment. B, ger- 

 minating seeds. C, 

 support and bottle 

 of potassium or 

 sodium solution. 

 D, rubber stopper. 



