TABLE IIT 
Analyses of Solutions 
NaNOsz Solution KCl Solution 
After Per After Per 
At Con- | AP- |cent.| at Con- | AP- | Cent. 
Begin-| tact | S°fP= | Ap- |Begin-| tact | S°TP- | ap- 
ning | with |4#10N bY) sorp-| ning | with |40DDy) sorp- 
Plant | Plant | tion Plant | Plant | tion 
D.p.M.| P.p.M.| P.p.m. p.p.M.} P.p.m.) P.p.m. 
Gales: 11 eis : 14 
TR eye iiatveteis [hoch euall hewn 1380 | 812 | 568 | 41.1 
INES 5 3} G80) SR) sXe | e283) 355 |) ses tae 
TT © Osi |e | Molds | see ereeeyerl| Gedling ieee 
CO] Leiria eens! boon ml pistes 1248 | 732 | 516 | 41.3 
NOs..| 1860! 335 | 1525/81.9]....!1 ... a6 
Barley plants grown seven weeks in complete nu- 
trient solutions. 
Contact with NaNO; and KCl solutions 39 days. 
balance. This ion in equilibrium with dis- 
solved CO, brought about a neutral reaction 
‘in the solution actually in contact with the 
plant. From the KCl solution K and Cl were 
absorbed in equivalent quantities. On the 
basis of these results it is clear that the 
selective action for NO,, while it does not of 
itself cause any injurious reaction, might 
eventually give rise to an alkaline condition 
in the soil as a result of the accumulation of 
Na,CO,. This is in accord with the usual 
conception. However, it is not easy to reach 
the conclusion that KCl, K,SO,, ete., could 
bring about an acid reaction in a similar 
manner. That such a result actually occurs 
in the soil as the result of salt treatments has 
been shown by Sharp and the author* and by 
Plummer,® but the increase in the intensity 
of acidity may be ascribed to interreactions 
in the chemical system of the soil, irrespective 
of plant absorption. 
The extensive analyses of Pantanelli® would 
indicate that in the case of almost every salt, 
after a few hours contact, the plant has ab- 
sorbed more of one ion than the other. Never- 
theless in the periods of time in question only 
4Sharp, L. T., and Hoagland, D. R., Jour. Agr. 
Res., Vol. VII., No. 3, pp. 123-145, 1916. 
5 Plummer, J. K., Jour. Agr. Res., Vol. XII., No. 
1, pp. 19-31, 1918. 
6 Pantanelli, E., Jahrb. f. wissen. Botanik, Vol. 
56, pp. 689-733, 1915. 
SCIENCE 
[N. 8S. Von. XLVIITI. No. 1243 
minute quantities were removed and the ex- 
change of ions between the plant and solu- 
tion was not excluded from consideration. 
The researches of Nathanson’? show the pos- 
sibility of such an exchange. For example, 
the absorption of NO, by certain alge may 
be accompanied by a loss of Ol from the 
plant. Nathanson emphasizes the necessity 
of a state of equilibrium in the solution and 
it is self-evident that the equivalence of posi- 
tive and negative ions must be maintained. 
Thus, if K is to be selectively absorbed from 
a KCl solution it must be as KOH, with a 
residue of HCl. The determinations of re- 
action and analyses of residual solutions are 
not in favor of this mechanism. It would 
seem the final result must be either the 
equivalent absorption of both ions or the ex- 
change of ions between plant and solution. 
In a complex nutrient solution or in the soil 
unlimited possibilities of combination exist. 
It is true of course that much evidence has 
been adduced by Pantanelli, Nathanson and 
others in support of the hypothesis of the 
absorption of ions as such, but no evidence 
obtained from ‘a study of the nutrient solution 
seems capable of conclusively demonstrating 
the precise mechanism of the intermediate 
steps in the absorption. Jn this general con- 
nection the universally known work of Loeb 
and Osterhout bearing on the ionic nature of 
antagonism will be recalled. In any ease, 
whether molecular or ionic absorption or ionic 
exchange is concerned the resultant solutions 
do not attain a concentration of H ion or OH 
ion indicative of the presence of highly dis- 
sociated acids or bases, while in complex 
nutrient solutions an approximately neutral 
reaction is produced as a result of absorption 
by the plant. 
II 
The nature of acid soils and their relation 
to crop growth have been among the topics 
most widely discussed by soil chemists. The 
common occurrence of soils distinctly acid (in 
the physical chemical sense) has been pointed 
7 Nathanson, A., Jahrb. f. wissen. Botanik, Vol. 
38, pp. 241-290, 1902-03; Vol. 40, pp. 403-442, 
1904; Vol. 39, pp. 607-644, 1903-04. 
