VOLUME XXXIx NUMBER 1 
bOLANICAT 9e W711i 
JANUARY, 1905 
THE EFFECT OF THE PRESENCE OF INSOLUBLE SUB- 
STANCES ON THE TOXIC ACTION OF POISONS. 
RODNEY H. TRUE and C. S. OGLEVER. 
Ir has been repeatedly observed in connection with the poisonous 
action of dissolved substances that the harmful effects are much 
more marked when the roots of the plants under test are immersed 
in the solutions than when these are grown in sand cultures which are 
watered with like or even more concentrated solutions (1). Upon 
this point the practice advocated by NAGELI (2) for removing traces 
of metals from distilled water may be cited. When to distilled water, 
rendered harmful for algae by the presence of traces of copper, crushed 
graphite, shredded filter paper, paraffin shavings, and other insoluble 
substances are added, the copper is removed from the water by some 
process dependent to a degree upon the amount of surface offered 
by the insoluble substance. 
In connection with experiments carried out in 1902 by TRUE 
and Grrs (3) at the Plant Physiological Laboratory at Woods Hole, 
Mass., on the modification of the action of poisons by the presence 
of other compounds, some preliminary experiments were made 
bearing on the effect exerted by the presence of insoluble materials 
on the behavior of seedlings of Lupinus albus. A concentration of 
copper sulfate was experimentally determined in which growth for 
twenty-four hours was possible, though at a somewhat diminished 
~rate. When to duplicate cultures insoluble substances were added, 
in nearly all cases a marked increase in the growth rate was noted. 
t After this paper was prepared, the line of argument and the evidence were sub- 
mitted to Dr. Lyman J. Briccs, physicist of the Bureau of Soils, U. S. Department of 
Agriculture. He has most generously given us the benefit of his special advantages. 
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