196 SECTIONAL ADDRESSES 
the forest was subdivided into working units called compartments, and 
for the sake of uniformity in working, these compartments were made 
as large as possible, with little or no regard to local variations in soil, 
climate and exposure. To a large extent the laws which govern tree 
growth and the possibilities of silviculture were ignored in favour of 
artificial formula. ‘This trend in forest management naturally led to a 
preference for pure stands—that is, large timber stands of the same species. 
The variation in species and age differences which characterise the 
primeval forest disappeared on its conversion into artificial forest, and 
much of the naturally associated flora and fauna was destroyed. It was 
easy enough to get so far, but difficulties arose when the questions of 
sustained permanent yield, conservation of soil fertility, and the repro- 
duction of this kind of artificial forest came to be faced. It is here that 
the inseparable connection between botany and forestry becomes all- 
important, and I hope to be able to show, by a brief reference to certain 
factors which govern tree growth, how important is the study of botany, 
especially plant physiology, ecology, anatomy, and plant geography, to the 
forester. In the northern hemisphere, from the subtropics to the Arctic 
and alpine limits of forest growth, certain well-defined climatic forest 
zones can be recognised. I here adopt Prof. Mayr’s subdivisions : 
the tropical forest zone, the Palmetum ; the subtropical zone of the 
evergreen oaks and the laurels, the Lauretum ; the temperate warm zone 
of the deciduous broad-leaved forest, warmer half, the Castanetum ; the 
temperate warm zone of the deciduous broad-leaved forest, cooler half, 
the Fagetum ; the temperate cool region of the spruces, silver firs and 
larches, the Picetum, the Abietum or the Laricetum ; finally, the cold 
region of dwarf trees and scrub, the Alpinetum or the Polaretum, Each 
tree has a certain natural range of geographical distribution. By ‘ tree’ is 
meant anything not less than 25 to 30 ft. in height. It has a cold limit, 
a warm limit, and between these an intermediate or optimum region of dis- 
tribution. ‘The factors which make up climate—e.g. such as temperature, 
aqueous precipitations, relative moisture of the atmosphere, and light 
intensity—vary from the optimum to the’cold-and-warm-range limits of 
each species, and the trees react accordingly. ‘The optimum region is 
where the general balance in climatic factors is the most favourable, but 
deficiency in any one growth factor may be made good or compensated 
for by the more favourable condition of other growth factors. It happens, 
however, that as a general rule, ultimate height growth, diameter incre- 
ment, volume production, form of bole, crown balance and development, 
seed production, and ease and certainty in establishment and after care 
are less troublesome and less costly in the optimum than elsewhere. In 
the southern or warmer climate, rate of growth is, to begin with, quicker 
than in the optimum, but it falls off sooner and, about middle age, rate of 
growth falls behind that of the optimum. Hence to obtain the best 
results in the cultivation of any species we must study its growth and 
habit and form throughout its entire range of natural distribution. This 
brings us now to the question: Is there such a thing as acclimatisation, 
or do trees possess the property of adapting themselves to climatic con- 
ditions which are new or different from any climate within their natural 
