118 CHRISTISON—OBSERVATIONS ON 
communts is under suspicion in regard to health, as its increase 
diminished year by year in place of increasing as it ought to have 
done in so young a tree; but taking the first year, when the 
increase was all but an inch, the distribution in the half-seasons 
was nearly the same as in the total period of four years. 
_As to the distribution in the four most reliable species, it may 
be pointed out that it is well spread over the season in all of them. 
Even in Rodznia, which shows such a decided preference for the 
end of the season, the increase began in April in five years out of 
six. In Saé/sx the spread is more equable over five months than 
in any other species under my observation, and although the 
proportion for April, the remaining month, is small, it is quite 
appreciable. 
The highest records for the months are—for April, 7°5 in 
Quercus Cerris ; for May, 18 in Q. Cerris ; for June, 33°5 and 33 in 
Ulmus and Pyrus ; for July, 36°5 in Q. rubra; for August, 34 in 
Robinia ; and for September, 10°5 and 10 in Rodzmza and Salsx. 
The lowest—in April, 1°5 in Pyrus; May, 9°5 in Robinia ; June, 
16 in Robinia; July, 25 in Rodinia; August, 15°5 and 16 in’ 
Pyrus and Q. Cerris; September, 1°5 in Q. rubra. 
D. Bi-Monthly percentage of Increase in the Single Trees 
of Twenty Species, 1891-95. 
The last form in which I show the comparative proportions of 
the monthly increase in girth of the different species is in bi- 
monthly periods for the twenty single trees of the set 1891-95, 
Table VIII. As previously explained, some of these trees are 
less reliable than others, but I give the whole for what they are 
worth. A few of the chief results may be pointed out. 
In the first, or April-May period, a proportion of 20 p.c. and 
upwards, or one-fifth of the seasonal growth, was attained by five 
species, while in nine species it was below 15 p.c. The highest 
proportion was in Quercus robur, 28 p.c., and the lowest in 
Populus fastigiata, 12 p.c. 
In the middle, or June-July period, eleven, ora little above the 
half of the species, attained a proportion of above 60 p.c. of the 
seasonal growth, and in three the proportion was below 50 p.c. 
The highest proportion was 72 p.c. in Aser Pseudoplatanus, and 
the lowest, 40 p.c., in Robinia Pseudacacia, 
