114 CHRISTISON—OBSERVATIONS ON 
(b.) The distribution of the girth-increase over the growing 
season shows considerable variety in the Table, but it is difficult 
to indicate it systematically. One way is to set the three best 
consecutive months against the other three. The three best are 
June, July, and August, except in Fvaxinus, which prefers May, 
June, and July. The percentages then are as follows :— 
Three Best The Other 
Consecutive Three 
Months. 
Populus fastigiata, ors =a 88 p.c. 12 p.c. 
Fraxinus excelsior, oy cS 88 I2 
CEsculus Hippocastanum, a 85 15 
Fagus sylvatica,.. cone 84 16 
Prunus Padus, ... st or 81 19 
Quercus conferta, = oe 78 22 
Ulmus montana = 78 22 
Crategus Oxyacantha, a 775 22°5 
Betula alba, : aye ae 73.5 26°5 
But this chiefly shows that certain species accomplish a con- 
siderably greater part of their increase in the three chief months 
than others, and therefore have presumably a less general 
spread over the whole period, and the comparative wideness of 
the spread is better seen if we take the percentages in each species 
due to the months of April and September united, or at the 
beginning and end of the season. The order is thus :—Cvategus 
13 per cent., Quercus 12°5, Betula 85, Ulmus 7, Prunus 6, Fagus 
5°5, raxinus 5, Cesculus 4, Populus 3. The result is but 
slightly to change the order as obtained by the first process, and 
to show that on the whole the seasonal distribution is widest in 
Crategus, Quercus conferta, and Betula,and is most limited in 
Fraxinus, C&sculus, and Populus. A further examination 
proves that the limitation to a comparatively small increase is 
at both ends of the season in Populus, at the beginning of the 
season in Gsculus and Fagus, and at its end in Frarinus. 
To put the case in another way, it may be said in a rough way 
that increase in girth was going on with comparative vigour for 
five months in Quercus conferta and Crategus, for four months 
in Fagus, Gsculus, Prunus, Ulmus, and Betula, and for only 
three in Populus, Acer, and Fraxinus. 
