44 RELATION OF LIME AND MAGNESIA TO PLANT GROWTH. 
On March 7, when the experiment was closed, the plants in A pots 
were healthy, of good color, and with twelve to thirteen leaves; height, 
from 16 to 20 cm. Plants in L pots were nearly dead, apparently 
atrophied, with from two to three leaves, and were from 3 to 4 cm. 
high. For samples of these plants, see Pl. I. 
A very similar experiment was made as follows: To 20 kilograms of 
sand, washed with dilute hydrochloric acid, there was added nutrients, 
as in the preceding case, except that in the A pots the percentage of 
MgO as carbonate was increased, making the proportion of CaO to 
MgO as-10 to 1, while in the Z pots the proportion of.CaO to MgO was 
as 1 to 2, the total amount of the MgO being 1 per cent of the whole 
culture medium. The nutrient solution was added each week as in the 
previous case. The pots were watered with distilled water. 
On February 8 tobacco plants grown in rich soil, and about 5 em. 
high, were taken, the roots carefully washed, and set in the sand in 3 
pots of each series. In the remaining 6 pots barley was planted. 
On March 7 the tobacco plants in 4A pots were in healthy, normal 
condition, height 7 to 10 cm., of good color, thrifty, and with seven to 
eight leaves. The tobacco plants in & pots were stunted, 23 to 4 em. 
high, lower leaves dead or dying, upper leaves dark green, thickened, 
and wrinkled. The plants were apparently dying by atrophy; number 
of leaves, three to four. 
The barley in the 4 pots was 14 to 27 cm. high and in a normal, 
healthy condition. The plants in the @ pots were 4 to 5 em. high and 
diseased. | 
In these experiments the action of an excess of magnesia in the soil 
seemed to result in the cessation of growth in the plant and the thick- 
ening and wrinkling of the leaf, at the same time the leaf assumed a 
deeper shade of green and showed a tendency to curl. -The roots 
showed little development, were without root hairs, and after some 
time became shriveled, and assumed a dark brown color. 
To the pots in the preceding experiment marked 4 and containing 
1 per cent of MgO as carbonate there was now added enough CaO as 
carbonate to make the proportion of CaO to MgO in three as 1 to 1 
and in the other three as 2 to 1. This was done with the object in 
view of determining the effect of calcium carbonate in overcoming the 
noxious influence of an excess of magnesium carbonate. 
EXPERIMENTS WITH BARLEY. 
On April 21 the pots were planted to barley which was sprouting on 
the 26th. On May 7 the plants were of good color, but on the 8th 
became slightly yellow, and upon examination showed an unhealthy 
root system. On May 23 the plants were making no growth and were 
removed. ‘ 
On May 26 tobacco plants 7 cm. high were set in the same pots and 
barley was also replanted. June 4 the tobacco was making no growth 
