148 FORESTS, WOODS, AND TREES 
produced being increased in quantity and improved in 
quality by the admixture. Beech also resists wind well, 
and when mixed with other trees renders the crop wind- 
firm. It is also valuable in shelter belts. 
Masses of pure conifers, as of spruce, silver fir, larch, 
Douglas fir, etc., are liable to be attacked by fungi and 
insects ; and it is of great benefit to intersperse amidst these 
uniform forests, bands and groups of beech and other broad- 
leaved trees, which will intercept the spread of spores by 
the foliage, and check insects by harbouring birds. In this 
way, suitable spots for ash, oak, sycamore, and elm, mingled 
with beech, may be found throughout the conifer planta- 
tions. 
Natural woods of beech occur in the Chiltern Hills and 
in the North and South Downs on the chalk, and in the 
Cotswolds on oolitic limestone. Here beech is found 
thriving on shallow soil, the rock below being often covered 
with only a few inches of humus. The productivity of the 
Chiltern beech woods is well known. These are worked on 
the selection system, a section of a wood being taken in 
hand each year, and from it the largest stems are extracted 
by felling. On the spots from which the trees have been 
removed, there springs up an abundance of seedling beech, 
so that natural regeneration is readily effected, and no ex- 
pense is incurred in the establishment of a young crop by 
planting. Areas occur in which beech is pure, but it is 
often mixed with scattered ash, whitebeam, and cherry, the 
latter being often abundant, and occasionally large in size. 
Beech, after it has passed the young pole stage, should not 
be kept too dense upon the ground, as with complete canopy 
the leaves are slow in decomposing, and produce, especially 
on non-calcareous soil, an acid humus. The ground remains 
bare of vegetation or else becomes covered with moss, Aira 
fleauosa, and Melampyrum, plants indicative of impoverished 
soil; and the beech ceases to grow vigorously, while natural 
regeneration is impossible under these conditions. With a 
slightly open canopy, the leaves decay quickly, producing 
an alkaline or neutral humus; and the soil is decked with 
