Part II.] 
Caccia : Development of Sal. 
203 
whole woods. Moreover, the number may vary without appreciably 
affecting the basal area and volume of the whole wood. The determina- 
tion of the average number of stems per acre, corresponding to different 
ages, is of importance to the forester, particularly in connection with the 
preparation of Yield Tables : but owing to the restricted number of even- 
aged Sal woods the early collection of data bearing on this question be- 
comes difficult. 
In the case of uneven-aged woods, woods treated under the selection 
system, the determination of the normal proportion which should exist 
between the number of stems of the different age or diameter classes, 
and the percentage of trees in any class that may survive to pass into 
the higher class is of importance ; and the periodical enumeration of the 
growing stock in sample plots or compartments with this object in view 
has been duly prescribed. But data are not as yet available. A sug- 
gestion has been made that the areas covered by the crowns of the aver- 
age trees in each class should be measured, in order to arrive at the 
number of trees of each class that can stand on an acre. Such proce- 
dure is not likely to yield useful data, and the direct observation and 
measurements of small groups of trees will in all probability be found 
more satisfa-ctory. 
Owing to the abnormal condition of many of the Sal forests under 
systematic working, complete or partial enumerations of the stock have 
not as a nde been carried out at the time of the preparation of Working- 
Plans, the yield being prescribed by area. The following table, how- 
ever, shows the average number of Sal stems of each girth class per 
acre to be found in those forests which have been enumerated : — 
