THE GIRTH-INCREASE OF TREES. 113 
1st Half |2nd Half 
| Apr, | May. | June. | July, | Aug. | Sept. | igi. St 
| 
| | 
| Populus fastigiata, ae 1 9 23°5 | 36 285 | 2 | 385 66°5 
| Quereus conferta, | 9 | 9:5 | 205 | 345/93 | 35 39 61 | 
} i 
(Esculus Hippocastanum, | aes eo 30 33 22 p Soaee ate | i) Bee 
Fagus sylvatica,... ...| 1 | 105 | 81% | 30°5 22 45 | 48 i ees 
Crategus Oxyacantha,.. | 3°5 | 9513905 |25 |22 | 951 435 | 565 | 
Prunus Padus, .. s {49 ae} desk aect-as = dee | 
Betula alba, . | 85 118 | 28 } 255 | 20 5 495 | 50° | 
Ulmus montana, a» f Be | 15 | B86 | 25% | 20 5 49°5 | 50° | 
| 
| 
Fraxinus excelsior, ... | 45 | 225 40° | 25 7 05 | 675 | 325 
On referring back to the history of the species, where the 
averages for both periods, 1892-95 and 1887-91, are given, it will . 
be seen that in Gsculus, Acer, and Betula these averages are 
almost identical as regards the half-seasons, and that in general 
there is a close approximation even in the monthly averages. 
In Fagus, Fraxinus, Populus, Crategus, and Prunus the differ- 
ences in the two periods are greater, but it is only a question of 
degree, the general tendencies being similar. Quercus conferta is 
included, although no example was under observation in either of 
the above periods, because the three trees of 1884-87 yielded 
such large and steady results, all in harmony with each other, 
that the laws of girth-increase are probably as well established 
in it as in any other species. The specimen of U/mus montana 
observed in the last period proved an utter failure, but as the 
two of 1887-91 were very fine trees, I give the average as being 
probably reliable enough, although there were some considerable 
disagreements in details. 
The general result is that in Populus, Quercus, and Zsculus 
the difference in favour of the second half-season is large; in 
Fagus and Crategus it is comparatively small; in Uimus, 
Prunus, and Betula there is an equality, or nearly so; and in 
Fraxinus the advantage is largely on the side of the first half- 
season. Taking the extremes, the proportions are as 2 to I in 
favour of the second half-season in Populus, and the same in 
favour of the first half-season in Fraxinus. 
