CH. l] RESPIRATION. 3 



germinating barley to cover a piece of wet filter paper at 

 the bottom of the flask. Barley germinates well ia 

 winter: it should be soaked in water for 24 hours and 

 kept in damp air for 24 hours before use. A test-tube 

 T half full of strong KHO is introduced into the flask, 

 which is then closed by a sound tightly fitting rubber 

 cork. As the CO2, produced by respiration, is absorbed 

 by the KHO, the mercury in the beaker Hg is sucked 

 up iJie tube A. In starting the experiment it is necessary 

 to warm the air in the flask before the end of A is forced 

 into the Hg, so that as the air cools again the mercury 

 may be sucked a little way up the tube to a point which 

 will then serve as zero for subsequent observations. The 

 warming may be done by immersing the flask in water at 

 40° for a few minutes; or it may be warmed by the 

 hands. 



(3) Sachs' method^. 



Place 10 germinating beans in a jar A, fig. 2, closed 

 by an india-rubber cork pierced by two holes and fitted 

 with glass tubes. One tube is connected with an aspi- 

 rator BO that a current of air is drawn through the vessel 

 and keeps up continuous normal respiration. The other 

 tube serves to admit to the flask air free fi?om CO2; for 

 this purpose it is connected with a filtering bottle F 

 containing a few sticks of KHO. The air is admitted to 

 F through a tube T filled with soda-lime. In order 

 that it may be certain that no extraneous CO2 enters the 



1 Physiologic Vegetale (French Translation), 1868, p. 295, fig. 35. 

 Also Pfeffer's Physiologie, i. p. 349, fig. 38. 



1—2 



