154 BOTANICAL GAZETTE [AUGUST | 
Mention was made above of the yellow color of leaves on plants in affected 
areas. This condition is generally considered to be due to a lack of nitrogen 
in the soil; this in turn is a consequence of poor development of the bacterial 
ora. That such conditions prevail in the soil of these denuded or partly 
denuded hillsides was shown by the fact that in unlimed plots very few bac- 
terial nodules were found on the roots of legumes. Development of such 
nodules was practically normal, however, where lime had been added. 
Root systems were found to be small on unlimed soil. Both primary 
and secondary roots were short and there was only a small amount of branching. 
As a consequence, the whole root system formed a knob or lump which came 
in contact with very little soil and furnished poor anchorage for the plant. 
There was thus more danger of injury from drought and from strong winds. 
Results confirming those already described were obtained by liming soils in 
other localities, hence they need not be discussed here. 
The author’s idea of the causes of the deliming of soils and consequent 
inhibition of plant growth has already been stated. In a discussion of his 
results he considers these causes at some length. He finds, in the first place, 
that all the untreated soils really are poor in lime. Near the smelter this sub- 
stance was present to the extent of 0.012 per cent; in experimental plots along 
the sides of the valley it varied from 0.017 per cent to 0.04 5 per cent; under 
a spruce stand it was 0.038 per cent. 
Further investigation of these soils brought out the surprising fact that 
they were acid in reaction, instead of alkaline or neutral, as might have been 
supposed. It is known of course that wet moor soils are acid, but this has 
been found by BauMAN and SuLLy to be due, not to the presence of free humic 
acids, but to the power of certain substances in these soils to decompose salts 
by forcing acids out of combination and by absorbing the bases with which 
they were combined. These authors showed further that this reaction is 
brought about by the “absorptively unsaturated” condition of the cell walls 
of sphagnum. The acid character of moor soils depends, therefore, on the 
fact that the material from ‘which they arise is already acid. But there is 
good reason, says WIELER, for thinking that dry peaty soils originate in the 
same way as do those of sphagnum bogs; that is, the plant remains in the 
former case are acid, just as they were in the latter. This deduction was 
amply confirmed by tests on living leaves and needles, the same organs dead and 
still remaining on the tree, or covering the ground beneath these trees. | 
hat the acids set free in the manner indicated above are not neutralized 
or decomposed depends finally on the failure of microorganisms to do their 
usual work. From undecomposed organic remains acids are being washed 
out continually by rains. As soon as bacterial and fungal action begins these 
acids are broken up into harmless substances. In soils, however, where the 
acid content is steadily increasing, as in the region around the Frankenscharm 
smelter, the bases, most important of which is lime, are neutralized. As 4 
consequence, microorganisms do not thrive, and plant fragments and the soil 
! 
y; 
B 
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