DAMAGE TO TREES BY ACID FUMES. 703 



" Lime withstands smoke, but suffers from green aphis and 

 otlier pests, and looks shabby in esLvly autumn, as the leaves 

 fall early. Eobinia thrives for 30 — 40 years, but then dies 

 gradually, perhaps owing to the cold clay soil of the gardens. 

 Two oaks remain small and scarcely grow, but have kept alive 

 for over 50 years. Laburnum does well, and so do white 

 and red thorns. 



"Of shrubs, Aucuha japonka is^ best, and fruits freely, and 

 so do several varieties of privet. Lilacs and box do well, and 

 Mahonias fairly." 



Webster adds the following to this list : species of lihus 

 and Cotoneaster, Virginia-creeper, ivy and the vine, besides 

 Daphne Laureola, L., Skimmea japonica, liihes sanguineus, and 

 Jasminum nudijioruni. He also gives a list of trees suitable 

 for town-planting, that generally agrees with Sowerby's list, 

 but also contains the following: Ailanthus glandulosa, DesL, 

 Magnolia acuminata, L., Liriodendron tulipifera, L., Catalpa 

 speciosa, Engelm, Morus nigra, L. He states, however, that 

 horse-chestnuts, limes, and elms soon show signs of distress 

 when grown in smoky localities. 



According to the Belgian official report, the black alder 

 {Alnus glutinosa, Gaertn.) may be seen growing close to 

 chemical works, and in situations very much exposed to acid 

 fumes, but apparently suffering very little from them. 



In planting avenues, or parks, in a crowded city, however, 

 not only immunity from fumes has to be considered, but also 

 the nature of the soil, the desirability of the tree, and the 

 amount of shade it gives, and whether it bears radiation of 

 heat from the houses and streets. The poplar, having a 

 straggling crown and its branches being very brittle, is not 

 suitable, wliile limes, except Tilia licteroplujlla, Vent., are 

 liable to lose their foliage prematurely in hot dry summers. 

 Probably the plane and sycamore are the best trees for the 

 purpose. Of oaks, probably the Turkey oak {Qucrcus Cerris, 

 L.) is the only deciduous species which can at all resist the 

 smoke of a large city. Quercus Ilex is termed by Masters 

 a good town tree. 



In the Black Country, near Wolverhampton, Dudley and 

 Bilston, the air is at present not nearly so impure as was 



