90 TRANSACTIONS AND rnOCEEDINGS OF THE [Sess. LXii. 



to get the average diameter, and the quotient multiplied 

 by 31 to get the girth for the year. 



The continued increase in the four radii, the average 

 diameter and the girth for each year, are represented by 

 curves, where the co-ordinates are years, for the age of 

 the tree, i.e. horizontal co-ordinate or abscissa ; and milli- 

 metres for the girth, i.e. vertical co-ordinate or ordinate. 



The actual scale on the diagrams shown is 5 years to 

 one inch horizontally, and 100 mm. to one inch vertically. 



The curves for the four radii, average diameter, and girth 

 of each tree are represented for periods of 5 years, and 

 where collective measurements were made an average for 

 each quinquennial period has been struck. 



On separate diagrams a life-size section of each tree, 

 calculated from the four radii, and marked with rings every 

 10 years and at the cambium, has been drawn ; and on 

 these sheets, also, has been drawn a section of the ground 

 showing its gradient and the position of the tree. 



The following are the details of the specimens exam- 

 ined : — 



A. Common larch {Larix europcca, DC.) was situated at 

 the X. side of the Inverey road, and close to its edge, about 

 two miles to the west of Braemar, near the point where the 

 road runs to the S.S.W., so that the S. and W. sides would 

 receive most light. Immediately above were the lower 

 slopes of Morrone, which rises to a height of 2819 feet, 

 and the tree itself stood about 1200 feet above sea-level. 

 The ground sloped gently at first, and then precipitously to 

 the Dee on the N., the river being within a stonethrow of 

 the tree. 



Trees grew all round, and the only open ground was 

 towards the road, while from the slope of the ground there 

 was moi-e light on the N. than on the M. side. 



The S. radius measured 324 mm. 

 W 290 



„ K „ „ 239 „ 



„ K. „ „ 220 „ 



As shown by the curve for the increment of girth, the 

 growth for tlie first 6 years was slow, then came rapid 

 growtli up to l."j years, and a still more rapid growth up to 



