1760 AGRICULTURAL BOTANY, CHKMISTRV AND PHYSIOLOGY OF PLANTS 



though it already contained 25 times as much calcium and magnesium 

 as did the sand. Still sand would have an ameliorating effect when com- 

 pared with water cultures. JENSEN found that in quartz sand a much 

 higher concentration of salts was required to cause death than in water 

 cultures. 



It is quite generally believed that plants have to some extent a selec- 

 tive absorption. The results here seem to indicate such a condition, for the 

 dolomites used tend to go into solution in a molecular ratio, but the plants 

 failed to take them up in this ratio. The tendency of the plants imder 

 these conditions was to take up relatively larger molecular proportions 

 of magnesium than of calcium. Analysis of the plants show that they do 

 not necessarily take up calcium and magnesium in the same ratio as ap- 

 plied, as, for example, in dolomite C3 the ratio of calcium to magnesium 

 is 5 : 5.2, while the plants may and do take it up in a ratio of 5 : 7 or 5 : 3.95. 



In the case of the addition of 25 per cent of magnesite the ratio of cal- 

 cium to magnesium was 5 : 125, while in some of the plants grown in such 

 treatment the ratio varied from 5: 15 to 5: 21. Wheat grown in soil treated 

 with 6 per cent of dolomite showed in the tops a ratio of 5 : 9.x and in the 

 roots a ratio of 5 : 4.35, or for the whole plant a ratio of 5 : 6.3, while in 

 dolomite CI it was 5-: 4.8. Alfalfa grown in the same treatment showed for 

 the entire plant a ratio of 5 : 4.2, but when grown in soil treated with 

 dolomite C3 the ratio for the total alfalfa plant was 5 : 3.95. 



The chlorides of calcium and magnesium were more detrimental to 

 wheat and soybeans than were the sulphates at concentration, up to o.i per 

 cent of magnesium. This amount cf magnesium in the prepared carbonate 

 entirely inhibited growth whereas lower concentrations gave better gro\\i:h 

 than either in the sulphates or chlorides. 



WTieat 65 days old showed smaller percentages of calcium and magnesium 

 than did similar^ treated wheat at 53 days of growth, but the total amount 

 of these two elements in the plants increased with the duration of growth. 



Soybeans at maturity, or 80 days after planting, showed for the hay 

 higher calcium and magnesium contents than at 53 days of growth, except in 

 the case of the checks and those treated with extremely small quantities. 

 Some of the samples showt^d as much as 73 lbs. of calcium and 25.2 lbs. 

 of magnesium per ton when grown in a mixture of one-half sand and one-half 

 calcareous soil, but when grown in soil containing 35 per cent of magnesite 

 there were 22.9 lbs. of calcium and 42.3 lbs. of magnesium, per ton ; whereas 

 the checks contained 5.8 lbs. of calcium and 5.6 lbs. of magnesium. 



Wherever excessive amounts of magnesium were applied, there was 

 a characteristic appearance of yellow leaves. The uppermost leaves became 

 yellow and gradually died, while the lower leaves remained green. This 

 condition is characteristic of magnesium sickness and just the reverse of the 

 effects produced by translocation processes. 



The general tendency is for the percentages of calcium, and magnesium 

 in the plants to increase with theincrease of size in application. Likewise 

 a high magnesium content in the plant tends to accompany plant sickness. 



