KESPIRATION AND OXYGEN. 



13 



Table 1. — Respiration of roots and leai\ 



Cauvet (1880 : 113) demonstrated that roots constantly excrete 

 CO2 and that this excretion is weaker at night than during the day. 

 He also determined that the root does not absorb CO2 from the soil, 

 and that the CO 2 excreted has for its immediate effect the solution 

 of the solid matter of the soil for the use of the root. 



Schwarz (1883 : 135) at first assumed that the production of root- 

 hairs was suppressed in many plants because of lack of oxygen. 

 The addition of abundant oxygen to the water-cultures failed to 

 cause the production of hairs and he concluded that the absence of 

 hairs could not be ascribed to its lack. It seems probable, however, 

 that the amount of oxygen used was too great for growth. Van 

 Tieghem and Bonnier (1882) found that 7.976 gm. of peas, sealed 

 in air, yielded 3.82 per cent of carbon dioxid and reduced the oxygen 

 to 14.44 per cent in the course of 2 years. 



Bonnier and Mangin (1884 : 215, 220) pointed out that, in pro- 

 longing the sojourn of plants in containers, the respiration was no 

 longer normal. At the end of a certain time, when nearly all the 

 oxygen was consumed, fermentation proper entered and carbon 

 dioxide was released in great quantity without oxygen being ab- 

 sorbed. They were also (1885) the first to show that respiration 

 increases with increased humidity of the air. 



