A PEDUNCULATED AND A SESSILE OAK. 
249 
This makes the graphic method the most satisfactory one from 
which a definite idea of the annual rate of growth can he obtained. 
Then the trees have been measured in two places, at 3 feet and 
5 feet from the ground. The proper height at which to measure 
the circumference of a tree has been discussed before our Society by 
the Rev. Canon Gee, ifl and he approved of the late Lord Yerulam’s 
“rule of thumb,” the height of one’s waistcoat-pocket; but the 
height of each of our waistcoat-pockets varies, and four feet is 
usually considered to be the proper height. I have therefore 
taken the average of the two measurements. I have also reduced 
the circumference to the diameter. 
Plotting the radius of the two trees at each measurement from 
a base-line representing the centre of each tree, on the scale of 
four inches to the foot, and drawing a line in the form of a curve 
through the points determined, somewhat freely in order to 
Fig. 25.—Segments of the triennial rings of growth of (a) Quercus pedunculata 
and (b) Q. sessiliflora for the 39 years 1865 to 190,4. 
eliminate certain irregularities which might be due to slight 
errors in measurement, the diagram now exhibited was drawn 
(this diagram is not reproduced here). The two long curved lines 
show the increase in radius of pedunculata and sessiliflora at 
four feet from the ground for the 39 years 1865 to 1904. The 
two shorter curved lines are portions of these superimposed, showing 
the rate of growth of the two trees at the same ages, from 54 to 
64 years of age. These show how sessiliflora from the age of 54 to 
that of 64 has rapidly gained upon pedunculata , but they also show 
that at the age of 54 pedunculata had attained a slightly greater 
diameter than sessiliflora. Its growth up to that age was therefore 
rather more rapid. This is perhaps more evident from the next 
two diagrams exhibited, which represent the rings of growth of each 
tree triennially for the whole period, and the annual rings from the 
54th to the 64th year of their ages. 
* ‘ Trans. Watford Nat. Hist. Soc.,’ Yol. II, p. 7. 
