124 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



noticeable in the early part of the season, no doubt because, at 

 that time, east and north-east winds are more prevalent, and 

 drive the smoke of the city over the place. On several occasions 

 in recent years this was veiy noticeable. It so happened that, 

 when the earlier trees had just got into full leaf, we had a 

 continued spell of east wind, with the result that the foliage was 

 very seriously injured. The leaves in many cases no doubt 

 suffered from other causes, which was shown by the edges 

 becoming brown, but there were also decided symptoms of the 

 effects of acid in the manner already mentioned, with very serious 

 results as regards the health and appearance of Horse-Chestnuts. 

 Their growth was entirely stopped until after mid-summer, when 

 Nature, trying to recoup herself, sprang away with a young 

 growth, rather a rare occurrence with these trees, which gave 

 them a somewhat remarkable and not altogether pleasing appear- 

 ance. Among forest trees. Oaks (particularly the Moss-cupped 

 or Turkey Oak) seem to withstand or resist the attack of acid 

 better than any others. Ash may be said to come next, followed 

 by Elm and Sycamore. The Ash, however, has a decided advantage 

 over the others, in that it is generally the last to put forth its 

 leaves, and casts them early, thus having them exposed for a 

 shorter time. Service trees, Birch and Rowans, especially the 

 two former, are also well suited for growth in smoky localities, 

 and are not so partial to a good soil as the others mentioned. 



What has been said is chiefly applicable to broad-leaved, and 

 especially deciduous trees. The same form of injury is, however, 

 not wanting among conifers, although possibly on the narrow 

 leaves it is not so apparent at first sight. On careful examina- 

 tion, however, the leaves are frequently found spotted in the 

 same manner, and at times the spots go right round the needles, 

 and cause the outer portion to die off, giving the injury the 

 appearance of that caused by frost. The result in both cases 

 is the same, the green living matter being killed, the power of 

 the plant for carbon assimilation is reduced, and causes the leaves 

 to fall prematurely. The balance of nature is interfered with, 

 and the health of the trees in this way seriously impaired, 

 making them more susceptible to attack from other causes, either 

 by insects or fungi, especially the latter. Attacks by insects on 

 conifers are fortunately less frequent on the trees which are most 

 affected by smoke than one would expect. Indeed those insects 

 which breed on sickly pines are conspicuous by their absence in 

 this locality. Although they are occasionally found, there has 



