262 RESPIRATION, FERMENTATION AND DIGESTION 



Close the stopcock a and if the level of the mercury in the 

 manometer arm remains stationary the joints are safe. Now re- 

 store the mercury above the stopcock a and allow the prepara- 

 tion to stand for two or three hours. Open the stopcock at a, 

 leading into B, and draw all of the air out of the tubes, then 

 turn the cock and force it into the open. Air for testing now may 

 be withdrawn in the same manner and forced into a test-tube 

 filled with mercury ; analyze with the Bonnier and Mangin ap- 

 paratus (Fig. 127). I to 2 cm. of the gas will be sufficient and sev- 

 eral calibrations should be made from it. The tests will give the 

 data for the respiratory quotient. Disconnect and draw air 

 through the preparation for a few minutes, then allow to rest two 

 or three hours, and make a second or third test. Comparative 

 tests should be made at identical temperatures. 



An error in such tests consists in the absorption of the watery 

 vapor in the air by the potassium solution, but this will not 

 greatly vitiate comparative tests. 



After one calibration has been made, disconnect the apparatus 

 and wash out the dextrose from the culture and replace with 5 

 per-cent. solution of tartaric acid, and repeat tests. 1 



330. Respiration of Oily Seeds. Soak about 200 cc. of seeds 

 of hemp for a few hours in water, then place in the receiver, make 

 an estimation of the proportions of carbon dioxide and oxygen 

 at the beginning of the experiment and four hours later. 



331. Respiration of Peas, Place about 200 cc. of germinated 

 peas in the receiver as above and estimate the oxygen and car- 

 bon dioxide at the beginning and end of a four-hour period. 

 Interesting results may also be reached by using a number of 

 flowers, mushrooms, or etiolated plants instead of seeds. 



332. Production of Heat in Respiration. Secure two strong 

 cardboard boxes of a capacity of about 600 cc. and cut slits in 

 the sides so that the bulbs of a differential thermometer may be 



1 Puriewitsch, K. Physiologische Untersuchungen iiber Pflanzenathmung. Jahrb. 

 Wiss. Bot. 35 : 573. 1900. 



Palladine, M. W. Influence de la nutrition par diverse substances organiques 

 sur la respiration des plantes. Rev. Gen. Bot. 30 : 18, 93. 1901. 



