130 M. M. McCooL 



" Magnesia in a soil in great excess over lime in a finely divided or 

 soluble condition is noxious to the growth of plants. "With a great excess 

 of lime over magnesia the physiological action of the plant is hindered and 

 it exhibits phenomena of starvation. An excess of lime counteracts the 

 poisonous effects of magnesia, while the more favorable proportion of the 

 two bases obviates the poor nutrition of the plant. 



" The best proportion of soluble lime to soluble magnesia for the germi- 

 nation and gro"v\i:h of plants is about molecular weight 5 to 4, or actual 

 weight 7 to 4. 



" In liming soils the amount of lime and magnesia should be first deter- 

 mined in both the soil and the material applied. In this way only can the 

 process be intelligently carried out and the best ratio between the two 

 bases for the promotion of the growth of crops be maintained." 



Meyer (1901) grew oats, potatoes, horse beans, vetch, and a mixture of 

 equal amounts of rj^e grasses and alfalfa in pots of a capacitj^ of six kilos, 

 which contained, on the one hand, sand and peat (2| per cent) and, on the 

 other hand, sand and loess loam (10 per cent). 



In the case of the oats-and-grass mixture, an application of gypsum at 

 the equivalent rate of more than one gram CaO per pot caused a decided 

 reduction of yield. The injurious effect of the g^^psum was overcome by 

 applications of calciimi carbonate or magnesium carbonate. 



Large applications of magnesium carbonate depressed the yield of the 

 grass mixture. It was observed also that even when an excess of lime had 

 been applied magnesia caused an increased yield. 



With pot experiments Aso (1903) found that the ratio of lime to mag- 

 nesia for the mulberry tree is about two or three parts of lime to one part 

 of magnesia. An excess of magnesia over lime retards gro'^iih. In some 

 experiments with rice Aso (1904) used in pot cultures soil that was taken 

 directly from a paddy field. To these cultures were added varying amounts 

 of calcium carbonate and magnesite. From the results obtained with this 

 crop Aso concludes that the ratio of lime to magnesia for maximum growth 

 is about the same as that most favorable for other Gramiiiece, which is 

 between 1:1 and 2:1. 



Kanomata (1908) found that " when the amount of lime is increased in 

 undue proportion to the amount of magnesia present, the yield of oats is 

 considerably depressed. In sand culture, there was a decrease by 39 per 

 cent of the weight of shoots before flowering time, when the amount of 



