16 BOTANICAL GAZETTE [JANUARY 
by a series of eight cultures, successively planted in different quan- 
tities of poison. Thus, seedlings lived in 1°° HCl ”/1024 for the first 
day, and not in quantities more than 1°°; while at the end of the 
eight successive plantiags in the same solutions seedlings were able 
to survive on the eighth day in 12° HCl ”/1024; hence definitely 
proviag that each successive planting reduces the toxicity of the 
solution. He says this is due to exudations of substances from the 
“oot. These same exudations furnish organic material for the 
srowth of fungi, which (as was also my experience) are very apt to 
make their appearance in a few days. 
BREAZEALE (5) made soil extracts of unproductive soils. To 
these extracts, filtered through a Chamberland filter he added various 
solids, such as ferric hydrate, calcium nitrate, calcium carbonate, 
carbon black, and fine quartz flour. He found that ferric hydrate 
and carbon black produce abaormal lengthening of roots, while the 
quartz flour does not. In his experiments on maize with sulfuric 
acid n/2750 to n/3250 prevented growth. Quartz flour did not 
change the apparent death limit. Clear sand, bits of filter paper, 
and paraffin shavings showed similar results with H,SO,. His 
results thus far, therefore, are diametrically opposed to those of 
True and OGELVEE. With CuSO, on the other hand, carbon 
black reduced the toxic effect. My own results, in so far as quartz 
flour is concerned, showed almost invariably that it reduces toxicity. 
The only exception is in phenol and alcohol. 
Materials 
Ground quartz, or quartz flour, of the grade commercially known 
as 5/o, which is a very fine powder, was the soil medium used. Wire 
baskets 88°™, paraffined and covered as described by LrvincsToN 
(27), formed the pots for the soil cultures. 
For the solution series, 500°° bottles with a wide mouth were 
generally used. A smaller dark bottle, of 70°° capacity, was also 
used, but did not give as uniformly good results as the larger bottle. 
The wheat used throughout these experiments was obtained 
from the Bureau of Soils, Washington, D. C., through the kindness 
of Dr. Lrvrncston. It is the variety kaown as Chul, grown in 
Utah, and was brought from central Turkestan by Dr. Ernst BESSEY. 
scien A 
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