1915] 



II A K I 'E 1 r —E Til YLENE 



209 



of osmotic pressure under such conditions have apparently been 

 made. 



Results with KN0 3 and glycerine indicate probably two things: 

 first, that neither the treated nor the untreated tissues are very 



TABLE IX 



Osmotic pressure and permeability 



permeable; and, secondly, that the treated tissue is slightly more 

 permeable than the control. 



D. RESPIRATORY CHANGES 



For the study of respiration, the cultural methods differed in 

 some respects from those already described. When the epicotyls 

 had become 2-3 cm. long (that is, read}- for the usual 72 hours' 

 exposure period), the entire seedlings or the epicotyls only were 

 taken from the pans and placed in test tubes of 20 cc. capacity, 

 graduated for 15 cc. The condition in the test tubes were as fol- 

 lows : They were filled with mercury and inverted over a dish of the 

 same. The mercury in the tubes was displaced to the 15 cc. mark, 

 either with pure air or an ethylene-air mixture containing 0.0002 

 per cent ethylene. Three entire seedlings or four epicotyls were 

 introduced from below into the various tubes. The experimental 

 periods were 3, 6, 12, 24, 48, and 72 hours. At the close of a period 

 the seedling or epicotyls were withdrawn by means of a hooked 

 wire and the gas present preserved for analysis. The Bonnier 

 and Mangin apparatus was employed for the gas analysis, fol- 

 lowing practically the procedure suggested by Thoday (32). 



