EXOTIC TREES IN GREAT BRITAIN 129
a height little short of 150 feet and a diameter of up to six feet.
At one time it was extensively planted for timber and for orna-
ment, but its susceptibility to diseases has made it unpopular
and it has given way to other species. In any case, its timber is
of little value but it is one of the few coniferous woods which
burn quietly, without throwing out sparks, when used for firewood.
The European Larch (Larix decidua Mill.) was also intro-
duced into Britain from Europe at about the same time as the
Silver Fir. Since then it has been widely planted and is almost
characteristic of the British countryside. Larch was extensively
planted in Britain in the 18th century, Scotland leading the way;
it is now one of our most important coniferous trees and certainly,
with the exception of Yew, yields the best timber—a wood which
is hard and heavy and of which the heartwood is very durable.
Apart from the value of its wood, its popularity with foresters
depends largely on the fact that the tree can be utilised at all
ages ; thus the first thinnings of a new plantation are suitable for
stakes and hop poles, older ones for estate work like fencing and
gates and for pit props, while the mature tree yields a wood used
for a variety of purposes ranging from boat building to flooring
and railway sleepers. The European Larch suffers from a num-
ber of diseases, one of the most serious of which is the Larch
canker, produced by an ascomycete parasite (Dascyscypha
Willkommii (Hartig) Rehm.). The Japanese Larch (Larix
Ieptolepis (Sieb. et Zucc.) Murr.) has been widely planted in
Britain, for it is relatively immune to canker; at least in its youth
the Japanese Larch grows faster than its European relative but
it is yet too early to prophesy how it will succeed in Britain as a
timber tree. There is evidence which suggests that in its later
stages the European Larch is the faster grower. Even more
vigorous is the Dunkeld Larch (Larix eurolepis Henry), a hybrid
between the European and Japanese Larches, and it appears to
be relatively free from diseases. Since, however, the first hybrid
seedlings were not raised until 1885, it is a little early yet to draw
conclusions as to the relative merits of these three larches. Where
its parent species grow in close proximity we may well find
seedlings of the Dunkeld Larch making their appearance.
The Pacific coast region of North America produces some
magnificent coniferous trees with a high yield of timber and it is
not surprising that British foresters should have decided to try
out some of these species under forestry conditions in this
country. On the whole it would appear that these experiments
are meeting with the success which they deserve, but it is rather
early yet to make many positive statements.
Of these North American trees the Douglas Fir (Pseudotsuga
laxifolia (Poir.) Rehder) is well to the fore and bids fair to