CURRENT LITERATURE 
BOOK REVIEWS 
Soil acidity 
The injury to vegetation by smoke from factories and smelters is wel] 
known. Much has been written on the subject, and considerable experimental 
work is now under way in various parts of the world. Wreter? has published 
recently an account of one series of experiments, begun in 1905, dealing with 
plant growth and the lack of lime in the soil. In this account he defends the 
thesis that smoke and smelter fumes are injurious to plants, not because of 
their direct effect on the leaves, but because the acid-forming substances they 
contain are absorbed in the soil and there neutralize the lime so necessary to 
plant growth. He argues also that there is an injurious effect on the micro- 
organisms of the soil. 
he region studied in greatest detail is a part of the Innerste Valley where 
considerable damage has been done by fumes from the Frankenscharrn smelters. 
The forest here has been driven back to considerable distances, amounting to 
3-5 kilometers in some directions. Even where trees were still standing, they 
showed by their stunted appearance and yellow leaves or needles the injurious 
effects of conditions surrounding them. Certain slopes bore only heath, low 
shrubs, and stunted trees, others only grasses, and still others no vegetation 
at all. Injury was greatest close to the smelter and decreased as the distance 
from the smelter increased. 
On the three kinds of slopes just described, experimental plots were laid 
out at distances of 0.5 to 1.5 kilometers from the source of the fumes. To 
these plots additions were made of lime, lime and ammonium hyperphosphate, 
and ammonium hyperphosphate alone. This substance was added on the 
supposition that the soil was poor in nitrogen. No striking results were 
obtained by its use, however, and it need not be considered further. Slaked 
lime was applied in finely ground form in quantities varying from 50 to 100 
kilograms per hectare. Untreated plots were studied as checks in all cases. 
Plantings were made of Picea excelsa, Pinus sylvestris, P. montana, Quercus 
robur, Fagus sylvatica, Betula alba, Vicia vi osa, and V. sativa. It was found 
in all cases that plants on unlimed plots grew much less rapidly and appeared 
less healthy than those on limed plots. Conifers and legumes either did not 
grow at all without lime, or only poorly. Oak, beech, and birch proved to be 
less rigorous in their requirements, but did better on treated plots.’ Plants 
from seed gave poorer resuits than those transplanted from the nursery. 

* Wreter, A., Pflanzenwachstun und Kalkmangel im Boden. 8vo. pp. vii+235. 
Sigs. 43. 1912. 
153 
