INFLUENCE OF TEMPERATURE UPON RESPIRATION 259 



tube until its tip projects into the gas (w). Turn the crank 

 wheel contrary to the movements of the hands of a watch, until 

 the gas fills about half of the free vertical portion of the capillary 

 tube. Remove the test-tube and force the gas on into the hori- 

 zontal portion of the tube (/). Read carefully the amount of 

 the gas in the tube (n). In the same experiment all readings 

 should be taken in the same part of the scale, as the tube may 

 not be exactly calibrated. Force the gas back into the bulb d. 

 Prepare a 25 per-cent. solution of potassium hydrate in distilled 

 water, in a test-tube over mercury. Introduce enough of this 

 solution into the capillary tube to about fill half the vertical 

 portion. Remove the test-tube and force both the gas and 

 solution into the bulb of the vertical portion at the left. Let 

 remain until the potassium solution has absorbed all the car- 

 bonic acid gas : a few minutes will suffice. Bring the gas back 

 in the tube and take another reading ; the difference between the 

 readings will be the amount of carbon dioxide present. 



The amount of oxygen can now be determined by introducing 

 a mixture of I part of 25 per-cent. solution of potassium hydrate 

 and 6 parts of 60 per-cent. solution of pyrogallic acid and after 

 manipulating as before, taking another reading. In atmospheric 

 gases the remainder may be taken to be nitrogen. The absorp- 

 tion solutions should always be freshly prepared. 1 



328. Influence of Temperature Upon Respiration. Prepare a 

 second lot of seeds as in 298 and when ready to place in the re- 

 ceiver, wash with cold water for five minutes and then set in place. 

 Fill the dish which is used to receive the displacing fluid of the 

 burette with a mixture of pounded ice and salt. Insert ther- 

 mometer in seeds, and close all fittings. Take readings of the 

 temperature every half hour for four hours. Make an estimation 

 of the carbon dioxide and oxygen present at the beginning and 

 close of this time. Compare with results obtained in 298. 

 Marked results may be obtained in three or even two hours. 



1 Bonnier and Mangin. Recherches sur la respiration et la transpiration des 

 champignons. Ann. Sc. Nat. Bot. 6. 17 : 210. 1884. Also, Recherches sur la 

 respiration des tissues sans chlorophylle. Same journal, 6. 18 : 293. 1884. 



