K.—BOTANY 199 
leaders—accident to the end bud of a leading shoot may cause double 
leaders, but that is a different thing ; in some the branches ascend at an 
acute angle, in others they tend to spread horizontally at right angles. 
Forking ‘eaders and spreading branches result in defective crown forma- 
tion. Another individual defect is the tendency to produce water shoots 
or epicormic twigs. Unfortunately this individuality does not seem to 
be hereditary, otherwise we could with greater certainty avoid such in 
selecting our growing stocks, but even if this were possible we would 
still have to face the fact that defect in stem, branch and crown and rate 
of growth is not due to individuality alone. Although the characteristic 
individuality remains constant throughout the life of each single tree, it 
does not follow that its seedlings will all possess the same characteristics : 
each seedling will have inherited an individuality, but not necessarily the 
same as that of the parent tree. Nevertheless, rate of growth and 
tendency to late or early vegetation become apparent early in the life of 
the seedling. It is then that the first choice can be made in the selection 
of growing stock. But no matter how perfect the young tree may be, it 
is still subject to the influence of external growth factors, and climate, 
soil and silvicultural treatment can influence its form and growth. A plant 
with individual tendency to slow growth in the colder limits of its dis- 
tribution will be stimulated to more rapid growth in the warmer climate ; 
and, on the other hand, a rapid-growing individual of the warmer climate, 
if transferred to the colder climate, will suffer check to its rate of growth, 
and individuals of normal growth will show the same tendency. Keeping 
these facts in mind, it is easy to see how readily false conclusions may be 
drawn in regard to the actual and relative rate of growth of different 
species. In a community of trees of different species growing on the 
same soil and in the same climate, some may be in their optimum, while 
others may be on the colder or warmer limits of their natural habitats, 
and the soil may suit some species better than others. If such an experi- 
mental plot were established by planting, allowance would have to be 
made for the time taken by different species to get over the check stage 
and to become completely established in their new quarters. Some 
species are quicker to re-establish themselves than others. That is, they 
are more easy to transplant. Then again, trees are not uniform in their 
rate of growth at all ages. We must, therefore, be careful in coming to 
conclusions regarding the growth behaviour of trees. We must seek the 
aid of plant physiology and plant geography if we wish to arrive at reliable 
and useful conclusions. Climate is after all the main controlling factor, 
and each country must collect its own data. Hitherto, in forestry, we 
have had to rely too much on data applicable to the continent of Europe. 
But with a well-selected series of representative sample plots established 
throughout Britain by the Forestry Commission, the arrears of our 
knowledge in this respect are being made good rapidly. 
Let us now consider the importance of these fundamental biological 
facts to silviculture. For convenience let us divide the life of the forest 
into three stages: the juvenile stage, the pole or stage of most rapid 
height growth, and the adult or tree stage ; and, in order not to obscure 
the main points by unnecessary detail, let us assume that the trees have 
