TOXIC LIMITS AND STIMULATION EFFECTS OF SOME 
SALTS AND POISONS ON WHEAT 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 
LXXXVIII 
G. H. JENSEN 
(WITH THIRTY-FOUR FIGURES) 
That the vital activities in plants may be inhibited or accelerated 
by many mineral salts has long been known in a general way. Hith- 
erto the problem has been attacked mainly from the standpoint of 
toxic solutions. The work which has taken into consideration the 
influence of a poison in soil has invariably been done with native 
soils. In these there are always present a great variety of chemical 
agents which may individually or collectively react with the intro- 
duced poison, and hence no fundamental conclusion can be deduced 
therefrom. TRruE and OGLEVEE in 1904 (42) showed that the 
toxicity of a solution was reduced by the introduction of solid insol- 
uble particles. This first suggested the possibility of comparing 
results obtained from plants grown in solution and in soil. The 
limited extent to which these authors carried their experiments, 
however, gave us no more than a suggestion of the possibilities. 
Previous experimenters, furthermore, have dealt mainly with small 
parts of the plants, such as the root-tips, determining their limit of 
endurance. 
The present work was undertaken with the purpose of ascertain- 
ing the toxic limit for the whole plant in both solution and soil cultures, 
and thus to make comparisons of the two conditions; to ascertain 
the effect of pure quartz sand in raising the toxic limit for a given 
poison upon the same plant; to add to the knowledge of stimulation 
effects of poisons in solutions; to discover whether these effects 
were also manifested in soil cultures; and to secure evidence of 
Comparative absorption of different poisons by the same sand. 
Historical ; 
The literature dealing with toxic effects on plants divides itself 
Haturally into two classes; first, that which deals with the lower 
on [Botanical Gazette, vol. 43 
