DAMAGE TO TREES BY ACID FUMES 701 



When exposed a second time for 20 hours, the silver-fir 

 needles absorbed T6 c. cm., beech leaves 3'1 c. cm. 



Webster* gives a list of trees and shrubs suitable for town- 

 planting, but among conifers only mentions the deciduous 

 Ginkgo biloba, or maidenhair tree, as flourishing in the worst 

 smoke-infected parts of London, and Retinospora plumosa 

 aurea, which has stood for seven years in one of the most 

 smoky districts of Glasgow, and looks almost as well as when 

 brought from the country. 



Masters also recommends Ginkgo Uloba, and Pinus excelsa. 



J. W. Sowerby, the Secretary to the Eoyal Botanic Society 

 of London, who has resided in the Botanic Gardens, Eegent's 

 Park, since 1842, states that when the gardens .were first laid 

 out (1839-45) special mounds were made and planted with 

 nearly all hardy species of conifers, and although the natural 

 soil of the gardens is a stiff yellow clay, suitable soil was 

 furnished for the different trees ; but in 1895, only a few 

 miserable plants remained, including five or six deodars, 

 and some yews, which last longest, but were then looking 

 very bad. 



The amount of damage done to broadleaved trees depends 

 not only on the susceptibility of the leaves, but also on the 

 powers of recovery of each species, so that trees which unite 

 least susceptibility to greatest powers of recovery will suffer 

 least. 



Schroder has drawn up the following list : 



1. Conifers : Silver-fir, spruce, Scots pine least susceptible. 



2. Broadleaved plants : Beech, lime, poplars, alder, maples, 

 ash, hornbeam, aspen, oak. 



The immunity of oak is not, however, confirmed by English 

 experience, and Marshall Ward states that oaks suffer greatly 

 from acid fumes. Perhaps the German authorities refer to 

 sessile oak, which is rare in England, where the pedunculate 

 oak abounds. 



A Belgian! official report also considers the hornbeam 



* "Practical Forestry," by Angus D. Webster. Eider & Son. 2nd edition. 

 London, 1895. 



f "Kapport par la Commission d'Enquete relative a l'influence des Emanations 

 Acides sur la Vegetation," quoted by Dr. Angus Smith in an appendix to " Air 

 and Rain." 



