250 
J. HOPKINSON—RATE OF GROWTH OF 
Segments of these two diagrams—a quadrant of one and an 
octant of the other, of each tree—are reproduced here on a much 
smaller scale as Pigs. 25 and 26. 
It will he seen (Fig. 25) that while sessiliflora has maintained 
a fairly even rate of growth, the increase of pedunculata has varied 
greatly and was decidedly less during the last half of the period 
than during the first half; and it is also apparent (Fig. 26) 
that while the growth of pedunculata increased in rapidity from 
the age of 54 to that of 64, that of sessiliflora decreased, although 
the tendency in sessiliflora is still to grow much more rapidly than 
pedunculata. 
Fig. 26.—Segments of the annual rings of growth of (a) Quercus pedunculata 
and (b) Q. sessiliflora from the age of 54 to that of 64. 
More definite conclusions might have been arrived at if the 
trees had been planted at the same time, for the rate of growth 
must depend somewhat upon meteorological conditions which vary 
from year to year. Temperature, sunshine, and rainfall are the 
chief variable climatic factors which influence vegetable growth. 
The ten years during which each tree has been measured at the 
same ages is a sufficiently long period to eliminate any appreciable 
difference in temperature or sunshine, but the case is otherwise with 
such a fluctuating element as rainfall. I therefore give a table 
showing the summer, winter, and yearly rainfall at Bayfordbury 
in decades for the whole period, from which it appears that at the 
same age pedunculata had the advantage of 3 per cent, more summer 
rainfall (in relation to the 40 years’ average) than sessiliflora , and 
11 per cent, more winter rainfall, giving a mean of 7 per cent, 
more annual rainfall, notwithstanding which its rate of growth 
was but little more than half as rapid. 
Decade. 
Summer, 
April-Sept. 
Winter, 
Oct.-March. 
Year, 
April-March. 
1864-65 to 1873-74 ... 
1874-75 to 1883-84 ... 
1884-85 to 1893-94 ... 
1894-95 to 1903-04... 
Ins. 
11-56 
14-22 
11-48 
ii-io 
Ratio 
95 
118 
95 
92 
Ins. 
I3-65 
13-66 
1 2* 11 
12*40 
Ratio 
106 
106 
93 
95 
Ins. 
25-21 
27-88 
23-59 
23-50 
Ratio 
IOI 
hi 
94 
94 
Mean . 
12-09 
100 
12-95 
100 
25-04 
100 
