Part IV.] Caccia : Selection method of treatment in India. 315 
Nevertheless in studying- the constitution of the normal selection 
forest the above fundamental principle may for the present be ac- 
cepted. 
The impossibility of determining the age of the various indivi- 
duals constituting the growing stock in a selection forest has led to 
the substitution of diameter- for age-classes. It is interesting 
therefore to consider what age periods the various diameter-classes 
may be presumed to represent. 
Theoretical considerations, based on the laws of the development 
of the diameter in even-aged crops, which have grown up under the 
conditions therein prevailing, wpuld point fn the conclusion that 
the rate of diameter growth diminishes very considerably in the 
older age-classes. This however does not appear to be the case in a 
selection forest. It will be readily admitted that in such a forest 
the trees grow up under very different conditions, and that it is not 
necessarily the oldest trees that are represented in the highest dia- 
meter-classes : but those trees which have grown up under the most 
favourable conditions for their development. In Europe the con- 
clusion now generally favoured appears to be that for any species 
tbe period passed in each diameter-class is the same; the trees in 
the highest diameter-class, if anything, growing (contrary to pre- 
conceived ideas) faster than those in the lower diameter-classes. 
And these conclusions appear to be borne out to some extent by 
such measurements as are available in India ; though it must be 
remembered that few of the forests at present under observation 
in India have grown up even under approximately normal selection- 
forest conditions. 
