Vol.VI., No. 53.] BULLETIN oF THE TORREY BoTANicaL Cus. [New York, May, 1879. 
§ 308. Notes on the Relative Age and Dimensions of a 
Number of Different Trees, 
The subject of the annual growth of trees is one about which 
little seems to be known in comparison with its importance. Of 
course it is generally believed that there is a difference in different 
species in the amount of this annual increase of dimensions, but 
there is apparently nothing on record as to any exact observations 
of the number of years which must elapse before we may expect a 
sapling to become a tree of given dimensions. Having had oppor- 
tunities during this past winter to measure a large number of trees, 
I have taken a series of notes on the subject, to the results of which 
I propose to call attention. 
And first a short description of the methods employed in obtain- 
ing the measurements will not be out of place. Three separate notes 
were taken from each individual tree examined ; (1) its age; (2) its 
height ; (3) its butt circumference. The age has been determined 
either from actual knowledge of the date when the trees were planted, 
or by counting the annual rings in the case of felled trunks, which 
latter may be a year or two in error in a few cases, owing to the 
difficulty in counting when the rings are obscure or very close 
together. In regard to the heights, trees which are still standing 
were measured by means of horizontal base lines and the corres- 
ponding angles of elevations, which were taken with a rough instru- 
ment and are approximate, the error in the height amounting to 
perhaps three feet in extreme cases. 
Trees which had been felled were measured directly by a tape 
line. 
The circumferences of the butts were measured, in most cases, 
at about three feet above the ground. 
These notes were tabulated, and those for each species averaged. 
Then assuming the section of the trunk to be a circle, average cir- 
cumferences were reduced to corresponding diameters. By dividing 
the average height by the age, the average vertical growth per 
annum was obtained. Applying the same operation to the average 
diameter, the quotient gives the average yearly increase in the thick. 
ness of the trunk, at its base, and one-half of this is the average 
thickness of the annual ring for that particular species. 
The notes were all nearly taken near New Dorp, S.[., over an 
area of perhaps three square miles, so that the differences in soil, 
rainfall, etc., must be small, and I think may be neglected. 
It is to be born in mind that the average rates of growth given 
in the foregoing table do not apply to the trees at every period of 
their existence. All trees grow much more rapidly vertically when 
. they are young; the yearly increase in diameter is a more constant 
quantity, but there is a’slight decrease in the ring thickness as they 
grow older, which is especially noticeable in the case of old trees, 
and where much crowding has taken place. N. L. Britton. 
