1908] BRIEFER ARTICLES 229 
be more fully demonstrated in a later communication, is practically the 
same. 
(3) The tolerance increases with the increase of the absorptive power; 
both factors being lower in the quartz, higher in the unmanured soil, and 
still higher in the manured soil_—JosEPH RosEN and CHARLES HELLER, 
Agricultural College, M: ichigan. 
