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is reached. The authors reached the important conclusion that 

 for any particular species this concentration is independent 

 of the nutrient salt used, as well as of the initial concentration 

 and the volume of the solution employed, provided the con- 

 centration is not too great to be toxic nor so low as to be in- 

 sufficient for the requirements of the plants for growth. The 

 concentration reached at equilibrium is, on the other hand, 

 specific for each plant. These conclusions are in rather sharp 

 contrast to those of W. Stiles and F. Kidd (Proc. Roy. Soc, B, 

 90, 448-70, 1 91 9) in regard to the absorption of inorganic salts 

 by a storage tissue — namely, carrot root. In this case the 

 initial concentration has a great influence on the equilibrium 

 concentration reached after absorption. It is, however, to be 

 expected that a root attached to a living plant and isolated 

 storage tissue should not behave in the same way. Similarly, 

 the latter authors have obtained evidence that the extent of 

 absorption depends very greatly on the nature of the salt 

 (Proc. Roy. Soc, B, 90, 487-504, 1919), the absorption of calcium 

 salts and sulphates appearing to take place to a less extent 

 than potassium and sodium salts and chlorides and nitrates. 

 Here also the difference in the tissues used is quite sufficient 

 to explain differences in the results. 



The absorption of boron has been incidentally examined 

 by F. C. Cook and J. B. Wilson (Proc. Amer. Soc. Biol. Chetn., 

 Journ. Biol. Chem., 33, vi-vii, 191 8). Plants are very specific 

 in regard to their absorption of boron compounds ; thus cereals 

 such as wheat, oats, and rye, absorb very little boron, while 

 succulent plants and plants of the natural order Leguminosae 

 absorb it in large quantity.' Not only does the absorption of 

 boron vary with the species of plant, it also varies with the 

 solubility of the boron compound and the concentration of the 

 compound in the soil, while it also depends on other soil factors, 

 such as the amount of water in the soil, the composition of 

 the latter, and so on. 



In a study, by H. S. Reed (Bot. Gaz. y 66, 374-80, 191 8), 

 of the absorption of sodium and calcium by wheat seedlings, 

 the antagonistic action of these two ions was demonstrated in 

 very dilute solutions. The experimental plants were analysed 

 at the end of the experiment, and the sodium and calcium also 

 determined in the culture solutions. The author finds that 

 there is no antagonism in regard to the absorption of the 



