124 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
is another strange fact, for, curious as it may seem, the smoke-proof 
London plane is by no means the best tree for either Liverpool or 
Warrington, particularly the former town, where the sycamore has 
been found to be far better adapted. In the very centre of Sheffield 
the Canadian poplar has been found to be by far the most useful 
tree, while in some of the worst localities in the colliery districts the 
chestnut and variegated-leaved sycamore are the greatest favourites. 
Even the rhododendron does well in the most smoky parts of 
the town of Bury, Lancashire. No better example could be 
adduced of how certain trees favour certain towns, than two or 
three kinds of poplars which grow with unabated vigour at Gatley, 
a small town near Manchester ; while at Bury, about equally dis- 
tant on the other side of that city, they positively refuse to 
grow, and that too after many unsuccessful attempts to get them 
established. Neither the rhododendron nor the laurel are at all 
suitable for the smoky districts of London; but casual observers 
may form a different opinion, from the appearance of such of these 
shrubs as are replanted annually, the semi-sickly subjects being 
replaced at stated times by those that are fresh and vigorous. In 
the smoky and impure (chemically) atmosphere of Glasgow the 
thorn and beam tree (Pyrus), as also several kinds of Retinospora, 
thrive amazingly, much better than they do in any of the large 
English towns, 
Why certain trees and shrubs succeed best in particular dis- 
tricts or towns is, perhaps, readily enough explained by the 
conditions of soil and situation, as well as the particular industry 
of the inhabitants. Coal smoke from the multitudinous chimneys 
of our larger centres of industry is no doubt bad enough; but 
when we have to contend with an atmosphere largely impregnated 
with the outcome from chemical, gas, or iron works, the difficulties 
to be encountered are great indeed. 
Preparation of the Ground and Planting.—In order that success 
may crown the effort, it may truly be said that no work of the 
horticulturist requires more skill and good management than the 
proper planting of trees alongside streets and avenues. 
The materials with which roads are usually made up are ill-fitted 
for sustaining a healthy condition in trees, at least for any great 
length of time, and this is well known to those who have taken 
any interest in the matter—broken stones, clinkers, and gravel 
affording but small support to vegetation, be it of whatever kind, 
but particularly large-growing trees and shrubs. Many failures in 
