INJURIES DUE TO ATMOSPHERIC INFLUENCES 301 



fresh shoots. Shoots are produced much better from the stools 

 of trees that have been entirely consumed, or that have been cut 

 over close to the ground directly after the injury occurred. In 

 such a case the whole of the plastic materials stored up in the 

 subterranean parts of the tree are at the disposal of the new 

 shoots. If the injured stem is sufficiently young to hold out the 

 prospect of stool -reproduction at all, it can only do harm to 

 delay cutting it over. 



SULPHUROUS ACID IN COAL SMOKE AND THE SMOKE FROM 



IRON-WORKS 1 



In the neighbourhood of extensive blast furnaces or similar 

 centres of industry, where large quantities of coal are consumed, 

 it has always been noticed that vegetation suffers from the 

 smoke. To such an extent is this the case that in industrial 

 towns like Essen scarcely any vegetation exists. In the direction 

 of the prevailing winds very serious damage is not unfre- 

 quently caused even for a distance of two miles from the fur- 

 naces. The views at one time held that the damage was due to 

 metallic poisons (arsenic, zinc, lead) present in such smoke, or 

 to the soot deposited on the leaves, have proved to be incorrect- 

 The investigations of Stockhardt 2 and Schroder 3 have shown 

 that the damage is due entirely to the sulphurous acid present 

 in the smoke. It has been determined by experiment that the 

 sulphurous acid being absorbed by the surface of the leaves 

 induces local death and brownness in the tissues. The tissues 

 prove most resistant in the neighbourhood of the larger ribs. 

 Although the leaves of conifers absorb less sulphurous acid than 

 those of dicotyledonous trees, still, on account of their being 

 longer exposed to the prejudicial influences, they generally 

 suffer more than the foliage of deciduous trees.* If one examines 



1 Hasenclever, Ueber die Beschddigung der Vegetation durch saure Case. 

 Berlin, 1879. 



2 Stockhardt, Tharander forstl. Jahrbuch, 1871, p. 218. 



3 Schroder, LandwirthschaftL Versuchsstationen, 1872 and 1873. 



* [I have investigated many such cases, and find the Larch suffers greatly. 

 The cases are complex, and it is by no means clear that the action of the 

 acid-gases is merely local on the leaves ; there is evidence to show that the 

 damage is largely due to the gases passing through the stomata and into the 

 lacunae of the living leaves. ED.] 



