1910) REED—TRANSPIRATION AND GROWTH OF WHEAT 107 
These results show, almost without exception, that the trans- 
piration and growth were accelerated by previously treating the 
soil extract with an absorbing agent; also, that the units of water 
transpired per unit of green growth were greater as a result of the 
treatment employed. In respect to their effect upon the resulting 
morphogenesis of the plant, the absorbing agents resemble such 
substances as pyrogallol. 
Discussion and summary 
The studies presented in the foregoing pages are devoted mainly 
to an investigation of the relation of transpiration to the green growth 
of the plant under the influence of various chemical agents. Higher 
concentrations of the chemical agents were avoided, since it is well 
known that a sufficiently concentrated solution of a non-toxic salt 
will retard growth and produce the effect of a “ physiological drought.” 
The small amounts of the respective chemical agents used had a 
definite influence upon the correlative transpiration. In the case of 
lime and sodium phosphate, the transpiration showed material 
increases, but potassium salts decreased it; while sodium nitrate 
was somewhat variable, usually operating however to cause a decrease 
in transpiration. Inorganic acids retarded transpiration, while organic 
acids were somewhat variable. Pyrogallol and tannic acid resembled 
the action of absorbing agents in causing large increases in the trans- 
Piration per unit of green growth. 
These effects appear in all cases to be a specific action of the ions 
Constituting any given agent. For example, K always showed its 
Inhibiting action on transpiration, regardless of whether it was com- 
bined with Cl, N O,, or SO,; so also was the accelerating action of 
Ca. In this respect the réle of these ions is doubtless comparable in 
Specificity with their réle in nutrition and other physiological pro- 
Cesses. 
The action of certain of these fertilizer constituents might be, 
as LAWEs suggested, of practical advantage in agricultural operations. 
Under more or less critical conditions, it is conceivable that the effect 
of a salt like K,SO,, which retards transpiration, might make an 
appreciable difference in plant growth. An experimental study 
of this question would be extremely interesting. 
