492 RELATION OF LIME AND MAGNESIA TO PLANT GROWTH. 
was reached resulted in the arrested development of the plant. The 
action of both elements were not in such excess as to vroduce a 
physical effect, but rather a physiological one. 
The experiments also show that potassium, sodium, and iron salts do 
not serve in the place of calcium salts in overcoming noxious effects of 
an excess of magnesia. In general, the potassium and sodium, both as 
nitrate and sulphate, seemed to reduce to some extent the toxicity of 
the magnesia, but not to such an extent as to justify their employment 
in actual practice. The iron sulphate, on the contrary, appeared to 
increase the toxicity of the excess of magnesia. Loew has already 
pointed out* that magnesia as nitrate and sulphate is alone more 
noxious to plants than sodium or potassium alone. 
In order to test the influence of an excess of magnesia upon the stem 
and foliage, a series of water cultures were made, using herbaceous 
branches, about 30 cm. in length, of the privet (Ligustrum vulgare). 
The solutions were made up and the results were as reported in the 
following table: 
Results of experiments with privet set August 23. 
| | August 23. September 15. October 4. 
| No. of |—— 
| bettle- | Solution. | ae Condition. | Condition. 
| | ent. 
29 | Distilled water ...-. | Ss ie NOGA As ee sae nee Normal. 
} 
30 | MgO as MgSQ,...--. 0.2 | Few upper leaves leit .--.--.- 
| 31 | MgO as Mg(NOz)o-- 0.2 | Stem blackened; leaves 
| | fallen. 
| 32 | CaO as Ca(NO3)o----| 0.2 | Leaves curled and mostly 
| fallen. 
| 
| | MgO as Mg(NOs3)o -- 0. | j oy ete mostly fallen; 
334 | Leaves slightly curled...... ‘ 
| CaO as Ca(NOs)o..-.| 0.1 color normal. 
| 34 | MgO as MgSQ,...-.-- 0.2 | Stem blackened; leaves 
| | fallen. | 
| | MgO as MgSQ,...... 0.1 | : , 
el eOjas Me ae loreal Be ie scas MAE Cy runs | Normal. 
|| CaO as Ca(NOg)o----| 0.1 || | 
| | | | 
From the foregoing tables it will be noticed that an excess of mag- 
nesium salts in the absence of calcium salts proved noxious to the extent 
of killing the plant. Where calcium salts were used without magne- 
sium the plant made a slow growth for a while, but Jater ceased grow- 
ing and exhibited phenomena of starvation—the development being 
arrested and the leaves assuming a light shade of green. Where the 
magnesium and calcium were used in conjunction, the plants in every 
instance made a healthy growth. In such combination the best final 
growth was made in a solution where the lime was in moderate excess 
of the magnesia, and the total amount of soluble salts, including 
nutrient, did not exceed 0.3 per cent. 
1Bul. No. 18, U. S. Dept. Agr., Veg., Phys., and Path.: ‘‘ Physiological réle of 
chemical nutrients.”’ 
