TREES IN TOWNS 51 
one-leaved ash (var. monophylla), are very distinct in appear- 
~ ance, and may be admitted into town parks and gardens. 
The ordinary species of lime, which have the leaves 
green on the under surface, namely, the common lime 
(Tilia vulgaris), the large-leaved lime (Tilia platyphyllos), 
and the small-leaved lime (Zilia cordata), are unsuitable 
for the centre of towns, as they do not thrive in smoke 
or drought. They are also objectionable in gardens, on 
account of the viscid honeydew which is exuded by their 
leaves. The silver limes, with leaves white beneath (Zilia 
alba and Tilia petiolaris), have not been much used in 
street planting; but they would succeed much better than 
the common species. 
The horse-chestnut, which is splendid in parks, is poor 
in streets, where it grows badly, as a rule, on account of 
the smoke and lack of moisture. As it comes early into 
leaf it is occasionally cut by spring frosts, which impair 
its vitality. Some people also object to its abundant fall 
of buds and flowers in the spring and of leaves and fruits 
in the autumn; but such debris is readily removed. In 
the streets of Paris the horse-chestnuts, which were formerly 
very fine, appear now to suffer much from smoke, which 
causes their leaves often to turn brown in summer and 
to fall off prematurely. The red-flowering horse-chestnut 
(Aesculus carnea) is a smaller tree of hybrid origin, which 
resists better unfavourable conditions of soil and atmosphere. 
Compact in habit, and bearing attractive flowers freely at 
an early age, it can be recommended for gardens in smoky 
towns. It succeeds well in Kensington Gardens, London. 
Of the numerous species of maple, the best for planting 
in towns is the Norway maple (Acer platanoides), as it does 
not attain a very great size, is compact in form, is remark- 
ably free from the attacks of insects or fungi, and withstands 
smoke well. It comes into bloom very early in the season, 
the conspicuous greenish-yellow flowers anticipating the 
leaves, whilst in autumn the foliage turns before falling 
a brilliant yellow colour. It is much more attractive in 
appearance than the sycamore or great maple (Acer pseudo- 
