CHAPTER II 
THE SANITARY INFLUENCE OF FORESTS 
THE protection afforded by forests or even by belts of trees 
makes life more bearable in districts where cold and humid 
winds prevail. Crops are enabled to grow which would 
not otherwise succeed; and domestic animals enjoy 
vigorous health, fatten, and produce an increased supply of 
milk (1). Very few persons, not excepting scientific men 
interested in ecology, have recognised the full severity of 
the effect on all living things of humid winds conveying 
air at a low temperature and persisting for a long period 
of time. The effect of such winds on trees themselves is 
most marked. Their stems are greatly shortened in height, 
becoming under extreme conditions unable to rise above the 
ground, as is well seen on the west coast of Scandinavia, 
Denmark, Holstein, Scotland, and Ireland. It is not the 
cold alone of the mountain summits or of the Arctic plains 
that stops tree growth, but the combined effect of wind, wet, 
and cold. 
In regions of extreme cold, if the air is still, there may 
occur large forests as in Siberia. Trees exposed to winds 
are not only lessened in height, but are also altered in 
shape, as they produce branches which grow best on the 
leeward side; and assuming what may be designated the 
‘flag’ form, they indicate the direction of the prevailing 
wind, which may be determined by the feeble or absent 
growth on the windward side. The injuries to trees, which 
are commonly ascribed to salt spray (2), are probably due 
entirely to strong wind, as may be ascertained by examina- 
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