182 INJURIES FROM SMOKE AND NOXIOUS GASES. 



adjacent tree slowly passes along the nearest root to the main roots, and 

 so slowly spreads. The dead trees are not injured for commerce, the 

 wood not losing any of its qualities by the death of its roots, if season- 

 ably used. 



The remedy appears to be — to wholly eradicate the itifected roots and 

 burn them. It might be prudent to surround a center thus affected by 

 a ditch deep enough to cut off all the roots, taking care to keep it free, 

 so that no contact could be had with neighboring trees. A mixture of 

 other species with the pine appears to prevent the disease, which has 

 only been observed where there are dense masses of the pine with no 

 other species. The beech appears to be also liable to the attack of this 

 l)arasite, and therefore would not be proper, although it grows well with 

 the pine. The spruce and the fir have not been observed to be injured 

 and might therefore be used, although their growth in a piuery is not 

 the best. 



INJURIOUS EFFECTS OF SMOKE, AND OF NOXIOUS GASES UPON TREES. 



It is well known that the emanations from certain chemical works, 

 and from lime-kilns, furnaces, and other establishments that send out 

 noxious vapors, will more or less injure the vegetation near them. In 

 cities, the deposit of smoke upon the leaves will more or less injure 

 their growth. As a general rule, trees with thick, leathery, and glossy 

 leaves are less injured by smoke than those having a downy or pubes- 

 cent foliage. But evergreens, properly so called (coniferse), will not as 

 a rule thrive so well, as they do not shed their foliage completely at any 

 time, and are not washeti clean by the rains. 



The following list has been given by an observer who has made this 

 subject a study, as comprising trees and shrubs that are best adapted 

 to smoky situations:^ Platanus occidentalis, Acer dasycarpum, Populus 

 haUamifera, P.fastigata and F.alba, Querents ilex, Tilia europea, Fraxiniis, 

 Eobina, Cytisus, Laburnum, Syringa, Ulmus, Lif/ustrum, Vinca, Vibtir- 

 man, Tinus, Philadelphus, Cratcegus, Ampelopsis hederacea. Clematis, 

 Aucuba japonica, Ailanthus glandulosa, Ficus carica, Gyd(mia japmiica, 

 Redera helix, Jasminum officinale, lihamnus alaternus, Ribes sanguinea, 

 Sophora japonica. Ilex aquifolium, Sambuciis, and Leycegteria formosa. 

 Among the palliative remedies proposed are the following : 



(1) Give more free space around each individual tree. 



(2) Prune early, regularly, and judiciously. 



(3) Soak well during drought the entire garden; and 



(4) Top-dress with fresh soil over the roots and shrubbery occasion- 

 ally. 



A short supply of water to the roots of trees, as well from the drain- 

 age of deep sewers — as from the closing of the surface by impervious 

 ])avementfi, concrete, and hard-trodden streets, appear to be active causes 

 of the stunted gTowth and early decay of trees in the streets of great 

 cities. 



Trees in parks and thoroughfares sometimes suffer from this cause, 

 their roots being prevented from receiving the benefit of rains. The 

 remedy is obvious, and the injury may sometimes be prevented by an- 

 ticipating the wants by jiroviding ample space of pervious soil above 

 the roots. 



The Platanus occidentalis appears to be particularly well adapted to 



1 Robert Hutchinson, of Carlowrie, Kirkliston, in a prize essay on the "Effects Pro- 

 duced ou Trees and Shrubs by Smoke from Public Worka<" Transom Highland and Ag. 

 Soc, 1876, p, 19l/ 



