1920] 
DUGGAR—H-ION CONCENTRATION AND NUTRIENT SOLUTIONS 39 
3 curves representing the results under the 3 combinations of 
conditions, as well as a fourth curve exhibiting the average of 
the 3 others. 
GENERAL DISCUSSION 
Hoagland (’17) determined the effect of H- and OH-ion con- 
centration on the growth of barley seedlings in an incomplete 
nutrient solution, omitting calcium, magnesium, and iron,— 
employing therefore only phosphates of potassium in some 
series and in others adding to these small proportions of sodium 
salts, including nitrate. The H-ion adjustments were made on 
the alkaline side with K;PO, and K:HPO,; on the acid side 
there was used KH;PO,, supplemented in one case by H;PO, 
and by the dibasie salt. As a result of numerous experiments 
he finds that a concentration of OH-ion greater than 1.8X10^ 
was injurious, and it was extremely toxic when the concentration 
reached 2.5x1075. A concentration of H-ion of X107? was 
favorable to growth while 3x107? was very toxic. In these 
solutions there was, of course, opportunity for antagonistic 
effects, and since the solutions were unbalanced, the injurious 
effect of the potassium or sodium ions or both would require 
consideration. 
Some of the complicated effects resulting from the addition of 
salts to toxie acid and alkaline solutions, especially in respect to 
the water relations of plants, have been dealt with by Dach- 
nowski (14); but inasmuch as the constituents of nutrient solu- 
tions were not involved either in control experiments or other- 
wise the data are scarcely applicable here. 
It is difficult, if not impossible, to attempt a comparison of the 
toxic action of H-ions and OH-ions from the dissocation respec- 
tively of mineral acids and such hydroxides as those of sodium 
and potassium in distilled water with the toxic effects produced 
by the same ions in a culture solution containing diverse other 
ions, especially the cations of the salts usually employed. In 
the latter solutions antagonistie effects, dependent in part upon 
specific relations of the plant employed, must to à certain degree 
obscure the magnitude of the effects. It is of interest to note, 
however, that Kahlenberg and True (96) found that roots of 
Lupinus albus just lived in n/6400 HCl. Nevertheless, after 5 
