128 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY, 



only a matter of time, it may be long or short, according to the 

 species or variety and its suitability to the soil on which it is 

 growing. The first sign is the early fall of the leaves, then the 

 crown gets thinner and the annual growth less, until it is 

 practically at a standstill, and gradually the tree dies a premature 

 death. Such symptoms are no doubt mainly due to the first- 

 named cause, viz., the presence of acid in the atmosphere — the 

 other causes lending their assistance, but certainly to a less 

 degree. On going farther afield, the injurious influences gradu- 

 ally become less discernible, and it takes a much longer time 

 before there is any serious result, unless with very susceptible 

 trees. 



From what has been said, I am sure anyone will assume that 

 the annual growth of trees is greatly reduced in smoky atmo- 

 spheres, pai'ticularly those in the immediate vicinity of the city, 

 but it is also quite noticeable a considerable way out, where the 

 traces of injury through acid are scarcely to be found. On Pollok 

 Estate I have watched this deficiency in growth with no little 

 interest for the last seven or eight years, and I calculate that the 

 different trees are afiected to something like the following extent 

 in the various woods and plantations — those nearer Glasgow 

 being decidedly the worst. With Oaks, Ash, Sycamore, Beech, 

 Elm, Hornbeam, Birch, Service trees. Rowans and Austrian Pine 

 the diminution in growth will vary in the difierent species from 

 10 to 20 per cent, in the immediate neighboui-hood, and farther 

 out it will not be more than something like 5 to 7 per cent. 

 If, on the other hand, the worst sufferers, such as Scots Fir, 

 Weymouth Pine and Spruce, are compared, it is found that in 

 plantations at the extremities of the estate, the annual loss in 

 growth is about 10 to 20 per cent., and in those near hand it is 

 as much as 25 to 40 per cent., and gradually getting worse. 

 Now if to this is added an equal reduction per cent, of stems per 

 acre, it is at once evident that it is absolutely impossible to culti- 

 vate trees successfully from a commercial point of view in any 

 smoky locality. In fact the great concern of those who either 

 own or manage woodlands under such conditions is not how to 

 make them pay, but how best to treat them so that they may be 

 kept in anything like a satisfactory state of health. I think no 

 one will deny that the smoke question as applied to the vegetable 

 kingdom is quite a serious problem, and any one who finds a 

 remedy will create a name for himself, and confer a blessing on 

 his fellow-raen. 



