296 Brenchley.—On the Action of Certain Compounds of 
checked with a less amount of poison than the shoots could stand. Once 
again 1/100,000 boric acid seemed to indicate the point at which the 
toxic action ceased and the stimulative action set in (Curve 16). 
gm. 
TohoJ 
Shooh 
Rool 
’ 100 40 20 10 ,5 3-3 2 -J 2 I *4 •«* 0 
i = r. 100,000 
Curve 16. Showing the mean values of the dry weights of ten series of pea plants (‘ Sutton’s 
Harbinger’) grown in the presence of boric acid and nutrient salts. (Aug. 29-Oct. 24, 1910.) 
gm. 
Curve 17. Showing the mean values of the dry weights of ten series of pea plants (‘ Sutton’s 
Harbinger ’) grown in the presence of boric acid and nutrient salts. (May 12-June 30, 1911.) 
The next year similar results were obtained, except in that the toxic 
effect of the acid was rather less evident ; 1/50,000 boric acid produced 
stimulation, which was maintained at the same level down to a concentra- 
tion of 1/25,000,000 B 2 0 3 . The slight difference in the two years’ results 
may be due to a combination of causes, such as the earlier date of the experi- 
ment (May and June) and differences in the seed and the season (Curve 17). 
Further tests in 1912 and 1913 bore out the general accuracy of these 
