14 BOTANICAL GAZETTE [JANUARY 
TABLE A 
Reagent Wheat Maize Barley Rye 
NaCl Germination prevented ky .| 0.20% | 0.50% | 0.25% | 0.40% 
ee Growth Lies nted b ° 0.25 0.20 0.20 
Na.CO Germination sueveicied by .| O.5=5.0) O.56 O. 0.50 
set Gro a ones ented by ...... 0.40 0.25 0.40 0.40 
Germination mca BY. -|: 1OrGEsS 0.02+ oe Ar 
NaS Growth prevented by ...... 0.005 0.02+ eee -% 
Naclo Germination Ler aig by 0.053 0.006+}] 0.007 0.006 
. se cb nted by... .... 0.003 0.004 0.006 0.004 
tion ainahio by..}| o.5+ 0.80+ o.60* 0.40 
Be), Gs Growth giant ara BY iole chic ©.10 oO. 0.10 0.30 
* Not effective. 
when added in finely divided particles to toxic solutions, markedly 
reduced the toxicity. They account for the reduction as being due 
to adsorption of poisonous particles by the substances introduced. 
In a recent paper LivincsTon (27) goes very fully into the physi- 
ological properties of a remarkably sterile soil, known locally as 
Tacoma Park soil. He concludes that some reagents, such as 
pyrogallol, calcium carbonate, and tannic acid, may act chemically 
upon the toxic bodies of the soil, while ferric hydrate and carbon 
black are merely absorbents of the same. 
KANDA (22) worked with solution cultures, and pot cultures 
of native soil. The latter were watered with poisonous solutions of 
the same salts from which his solution cultures were made. He 
was the first to show that ZnSO, is an active stimulant to higher 
plants. He did not observe stimulation with solution cultures of 
CuSO,, but soil cultures gave quite marked stimulation. The 
results that he records for Pisum and Vicia Faba in this respect agree 
with my own on wheat. 
HARTER (18) exposed wheat. roots for twenty four hours to toxic 
solutions. He found that varieties of wheat from arid regions of 
Russia, where the soil is alkaline, are more resistant than are those 
grown in more humid regions. The reagents used by HARTER 
were sodium carbonate, bicarbonate, sulfate, and chlorid; and 
magnesium sulfate and chlorid. His work therefore naturally 
suggests that relative toxicity of salts must be learned by experi- 
menting upon a single variety or strain; and to overcome errors due 
to individual variation many plants must be used. 
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