RESPIRATION AND OTHER FORMS OF METABOLISM. 45 



13.26 cc. of carbon dioxide in the same time, and I gram of seed 

 of Madia absorbed 15.83 cc. of oxygen, while it exhaled 11.94 

 cc. of carbon dioxide. Young growing plants will exhale an 

 amount of oxygen equal to their own volume in 24 to 36 

 hours. 



EXPERIMENT 51. 



EXCRETION OF CARBON DIOXIDE BY LEAVES. 



Provide a ground-glass bell-jar and plate. Under the bell-jar 

 place a well-leaved plant grown in a pot, and a vessel containing 

 lime- or baryta-water ; place the apparatus in darkness. After a 

 short time a film of carbonate can be seen on the surface of the fluid 

 which, if allowed to remain longer, collects as chalk (or baryta). As 

 a control experiment, set up the same apparatus without the plant. 

 The lime- or baryta-water is scarcely affected. (Fig. 39.) 



EXPERIMENT 52. 



EXCRETION OF CARBON DIOXIDE BY GERMINATING SEEDS. 



Fill a glass jar of i liter capacity one-third full of Peas which 

 have lain a day in water. Cover tightly. After 12 or 14 hours a 

 light thrust in is extinguished, showing the lack of oxygen, and a 

 vessel containing lime- or baryta-water placed inside demonstrates 

 the presence of carbon dioxide. Instead of Peas, developing heads 

 of a Composite or some large Fungus can be used. (Fig. 40.) 



36. Liberation of Heat. In very strong respiration, as in 

 the development of flower-heads of the Compositae, flower-tubes 

 of the Aroids, and germinating seeds, enough heat is liberated 

 in the combustion of the carbon compounds of the plant to 

 be easily detected by the thermometer. Sachs observed in 

 100 to 200 germinating Peas a rise in temperature of 1.5 C. 

 (Fig. 41.) 



EXPERIMENT 53. 



HEAT LIBERATED BY GERMINATING SEEDS. 



Fill a glass funnel of medium size with germinating Peas 

 or blooming heads of Leontodon, Anthemis, Bellis, etc., into which 

 a thermometer graduated to \ degree C. has been thrust. To avoid 



