592 Prof. H. E. Armstrong and Dr. E. F. Armstrong. [Apr. 29, 



We are therefore inclined to attribute the apparent activity of tlie two 

 ammonium salts to ammonia liberated by their hydrolysis, as the solutions 

 gradually become distinctly acid to litmus and to phenolphthalein ; it was 

 conceivable that the acidity might have been due to the diffusion of acid from 

 the leaf into the solution but this explanation seems to be precluded by the 

 observation that when the leaf is exposed in a 1 5-per-cent. solution of alcohol 

 no acid passes into the liquid. 



Action of Acids. — The leaf septum is affected by acids more readily than is 

 the barley septum, being destroyed by solutions of sulphuric acid of 

 N/20 strength and upwards, all of which condition the liberation of 

 hydrogen cyanide. 



Chlorhydric, phosphoric, tartaric and nitric acids are less destructive and 

 do not enter the normal leaf from N/2 solutions; oxalic acid is active and 

 formic, acetic, propionic and butyric acids pass readily into the leaf from 

 solutions of this strength ; lactic acid acts less rapidly than acetic ; benzoic 

 and salicylic acids (in saturated solutions) also are .quite active. Boric acid 

 passes slowly into the leaf from M/2 and M/5 solutions and after 100 hours 

 from M/10 solutions. 



The following substances are inactive in dilute solutions : — 



In 2-per-cent. solutions — In 5-per-cent. solutions — continued. 



Phaseolunatin. Potassium iodide. 



Salicin. „ phosphate. 



Arbutin. Ammonium oxalate. 



Amygdalin. „ sulphate. 



Formaldehyde. Copper sulphate. 



Vanillin (saturated). Barium chloride.* 



In 5-per-cont. solutions — Silver nitrate. 



Glycine (also in 7 per cent.). Magnesium sulphate. 



Asparagine. In N/10 solutions — 



Dextrose. Sodium carbonate. 



Sucrose. „ bicarbonate. 



Glycerol (10 ])er cent.). „ hydroxide. 



Sodium acetate. Barium „ 



„ borate. In M/10 .solutions — 



„ chloride. ('adnuuiii suljjhate. 



„ nitrate. „ chloride. 



Potassium borate. Mercuric nitrate. 

 „ bromide. 



It is clear from our oUservations, taken in connection with tho.se made by 

 Adrian J. P)rown, tbat all substances are effective which can penetrate the 

 colhiliLr niciiilirancs and v.uiv.v into tbe circulation. 



* Slight action was noticeable on exposing the leaf in a 10-per-cent. solution of this 

 salt <luring 100 hours. 



