vit] PLANTS AND ANIMALS. 129 
immigration of six new species of birds which feed 
upon insects. At Farnham we are shown the reason 
why the Scotch Fir, a thoroughly indigenous tree, 
cannot grow unless protected by enclosure. 
Speaking of the Scotch Fir reminds us of another 
change effected by man, by the introduction of foreign 
species. The Scotch Fir (Pznus sylvestris) is the only 
truly native species of Pine or Fir in Britain, and is 
held to be one of the most valuable of the European 
Conifere as a timber tree, producing, as it does, the 
best “deal.” But it is a slow-growing tree, and con- 
sequently the timber-growers of this country have to 
a large extent supplanted it by the introduction of 
the Spruce Fir (Adzes excelsa) and the Larch (Larix 
europea), more rapid growers. Previous to the Gla- 
cial Period the Spruce Fir was evidently a prosperous 
native of this country, but in recent geological times 
it was here unknown until its introduction three cen- 
turies ago. To-day it is as common as the Scotch 
Fir itself. The Larch is an even more recent impor- 
tation, not having been introduced in any quantity 
previous to one hundred and fifty years ago. Now 
large areas are planted with it. So rapid is its growth 
that Wordsworth called a plantation of it at Grasmere 
“the vegetable manufactory.” Now there is a vast 
difference in appearance between the Scotch Fir 
(which is really a Pine and not a Fir) and its sup- 
planters—the former being flat-headed, whilst the 
latter are conical—and the introduction and exten- ~ 
sive cultivation of the latter must have effected a 
considerable change in the landscape alone of 
Scotland. But we know that such an important 
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