Pee MAGE. 
Although liming of soils has been practiced for ages and is fairly 
well understood from the chemical and physical standpoints, compara- 
tively little has been done toward determining the exact physiological 
explanation of some of the beneficial and injurious effects of liming on 
the growth of crops. The physiological réle of calcium and magne- 
sium salts was briefly discussed in Bulletin No. 18 of this office on the 
Physiological Réle of Mineral Nutrients. In the present bulletin are 
brought together many valuable observations on the general subject 
of liming, especially from the standpoint of the plant. The work, 
though preliminary, shows quite clearly that magnesium salts are 
poisonous to our ordinary crops unless accompanied by readily avail- 
able lime compounds. Under the direction of Dr. Loew, Mr. May, of 
the Office of Experiment Stations, endeavored to determine experi- 
mentally the proper ratio of lime and magnesia for certain crops and 
soils. The results of these investigations warrant the statement that 
the amount of available lime and magnesia should be about equal 
in order to insure maximum growth for most crops. The subject is 
presented at this time with the hope that it may stimulate investiga- 
tions along these lines, so important to agriculture. We are under 
obligations to the Bureau of Chemistry for the chemical analysis of 
some of the soils and other material used, and to the Bureau of Soils 
for physical analyses. The manuscript of this bulletin was submitted 
for publication nearly a year ago, but it has not been practicable to 
print it until the present time. 
ALBERT F. Woops. 
OFFICE OF THE PATHOLOGIST AND PHYSIOLOGIST, 
Washington, D. C., June 17, 1901. 
