120 FOKESTS, WOODS, AND TREES 



Extensive plantations of conifers are liable to wide- 

 spreading attacks of fungi and insects, and to great damage 

 from gales and fire. It is advisable, then, to interrupt the 

 continuity of great areas of conifers by planting, at suitable 

 distances, wide bands of broad-leaved trees. Beech is the 

 most suitable species for this purpose ; but ash, sycamore, 

 wych elm, alder, etc., may be added in varying proportions 

 according to the nature of the soil. The influence of 

 broad-leaved trees is manifold. Judiciously distributed in 

 belts or in groups they act as wind-breaks ; they are 

 visited by birds which prey upon noxious insects ; and the 

 humus, due to their decaying leaves, brings health and 

 vigour to the coniferous tracts. Broad-leaved trees may 

 also be planted along the rides, rowan and grey alder being 

 of use at high elevations. 



We are not limited in our choice of species to our few 

 native trees. These are late immigrants from the Continent 

 after the glacial epoch, and are by no means the trees that 

 are most suitable to the climatic conditions of the present 

 day, or that are most fit for producing, as quickly as 

 possible, valuable timber. 



The Scots pine, our solitary native conifer of forest im- 

 portance, was widely spread over the British Isles in the 

 dry, warm, continental climate that prevailed at the begin- 

 ning of the neolithic period ; but it has, with the advent of 

 our present humid, cool climate, gradually disappeared from 

 all parts of the country, except in the mountain massif of 

 the Scottish Highlands. It is most suitable for districts 

 characterised by a low annual rainfall and much sun in 

 late summer and autumn, as in Speyside, Deeside, and Tay- 

 side in the north, and in the sandy heaths of the south and 

 east of England. In such districts it regenerates itself 

 freely, and attains a great height, producing a satisfactory 

 volume of timber of good quality. 



Fortunately we are not restricted to native trees. Dur- 

 ing the eighteenth century, spruce, silver fir, and larch from 

 the Continent began to be largely used in our plantations. 

 The movement towards extensive use of exotic trees was 



