168 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
it has been found that the monetary return is not only larger, but 
the seed-production is also much more favourable for natural 
regeneration, at from 50 to 60 years than at any higher rota- 
tion, owing to a very large proportion of the trees becoming dead 
in the crown and moribund from the attacks of canker-fungus. 
Throughout this region natural regeneration, it may be remarked, 
is obtained by leaving from forty to sixty seed-bearers per acre, 
while the soil is prepared by clearing away heather, bracken, etc., 
and working it up in strips or patches; and seed is sown in places 
where it has not been possible to reserve seed-bearing trees, 
while blanks are subsequently beaten up by planting. 
Although the mixed forests of France are less subject to 
insect-attacks than the pure woods of coniferous trees common 
throughout many parts of Germany, yet serious damage also 
occurs every now and then. 
On 1st February 1902, in the Vosges mountains, a hurricane 
in a few hours threw 43,175,000 cubic feet of coniferous timber- 
crops, of various ages, valued at £360,000. As is always to be 
feared under such circumstances, this has been followed by a 
sudden increase in noxious insects, among which the chief were 
Bostrichus typographus attacking spruce, and, to a minor extent, 
B. curvidens attacking silver fir. The former is to be found in 
British woodlands, but extensive damage has not hitherto been 
caused by it after cyclonic storms, probably owing to the com- 
paratively slight extent to which spruce is grown. But, if large 
plantations should ever be grown for pulp-wood, this is a danger 
that must always be kept in view, because one female can lay 
80 eggs, which may easily multiply into 3200 in the second 
generation, 128,000 in the third, and 5,120,000 beetles in the 
fourth, and this all in the space of two years if these happen to 
‘be dry and warm, although during cold and damp years the 
generation is usually only annual. In the present case there 
appears to have been two broods in 1903, and in that autumn 
the presence of an unusual number of the insects was noted, 
although it was not realised how serious was the danger they 
threatened. The position was only thoroughly apprehended in 
May 1904, when orders were immediately issued for taking active 
exterminative measures throughout the tracts infested, the trees 
were carefully examined, and those found to be attacked were 
felled, lopped, and barked, and the bark burned in large fires 
made with the branch-wood. It was not easy to distinguish the 
