218 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
in the culture solutions is noted, for protoplasm is coagulated differently 
by different reagents. For instance, osmic acid characteristically produces 
a net-like coagulum, 6 which differs materially from the flocculum observed 
in the present experiments. 
Although the argument above presented seems logical, it may be that the 
coagulation was induced by the chlorine ion, and that the sodium ion ren¬ 
dered it innocuous when sodium chloride was used instead of hydrochloric 
acid. The experiment was accordingly repeated with a 0.45 M solution 
of nitric acid, the anion of which was formed in the nutrient solutions by 
the dissociation of calcium nitrate. The results, shown in figure 4, duplicate 
the results that were obtained with hydrochloric acid and with the nutrient 
solutions of high phosphate concentration. The conclusion seems ines¬ 
capable that in every instance the coagulation is due to the hydrogen ion. 
A further experiment was undertaken to determine whether or not the 
presence of salts alters the rate of coagulation by the hydrogen ion. Root 
hairs were irrigated with solution 2 to which sufficient nitric acid had been 
added to make the concentration of acid 0.45 M, and note was taken of the 
time required to produce a degree of coagulation equal to that produced 
by the end of four and one half hours when an equimolecular solution of 
nitric acid in pure water was used. Of the two root hairs irrigated with 
nitric acid in salt solution, the protoplasm of one was coagulated to the 
extent defined above in four hours, that of the other in five hours. Since 
these results indicate a pronounced individual difference in root hairs, and 
since the effect of salts on the chemical potential of the hydrogen ion is not 
properly a part of the present thesis, the experiments were discontinued. 
The experiment is cited, however, and drawings of one of these hairs are 
shown (fig. 5), because, since the coagulation was produced in a nutrient 
solution, and since it is of the same kind as that usually produced in solu¬ 
tions of high hydrogen-ion concentration, although to a greater extent 
because of the added acid, it affords additional evidence, if that be needed, 
that the coagulation in the culture solutions is due to the specific effect of 
the hydrogen ion. 
It is now possible to explain the abnormal root development in those 
nutrient solutions that contain an injurious quantity of potassium di-hy¬ 
drogen phosphate. The hydrogen ions precipitate the protoplasm of the 
root hairs, which are the primary absorbing cells of the plant, thus increasing 
their permeability and rendering them unable to act as absorption organs. 
As the root hairs become ineffective, more are formed, as in dry soils or in 
culture solutions such as solutions 4 and 5, where the phosphate concentra¬ 
tion is too high. If the root cannot produce enough root hairs to carry on 
the work of the plant, which in turn becomes stunted, then more roots are 
formed, thus producing the short, branched root systems described above. 
This series of effects affords another 7 example of the Le Chatelier-Braun 
6 Bayliss (’18), p. 15. 
7 For other examples, see Bancroft (’n). 
