164 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



13. Observations in connection with Annual 

 Increment of growing Crops of Timber. 



By J. H. Milne-Home. 



Some notes upon this subject have been published in previous 

 numbers of the Transacfio?is (vol. xxiv. p, 52, vol. xxvi. p. 160, 

 and vol. xxvii. p. 34). The particulars there given relate only 

 to a period of three years, and the conclusions drawn from the 

 measurements which had then been made were admitted to be 

 provisional and tentative. These observations have been carried 

 on down to the present time, and certain fresh groups have been 

 subjected to measurement, so that the results now obtained are of 

 considerably greater value. The objects in view were twofold — 



(i) To ascertain with as much accuracy as possible the 

 percentage rate of increment for various ages and species of 

 timber, and (2) to ascertain during what season the actual 

 laying on of girth took place, and the proportion of growth 

 made during each month of the growing season. 



The method followed in making the observations has been 

 referred to in previous articles, and need not be repeated further 

 than to explain that the percentage rate of growth is calculated 

 by the formula employed by continental foresters, viz., per- 

 centage rate of growth in any year= -,; " ?i" is the number 



of annual rings in the last inch of radial growth, and "^" 

 the diameter under bark at 4 ft. 6 ins. from the ground. The 

 value of " ?i " could at first only be estimated from one or two 

 years previous growth, but as the yearly observations went on 

 it was possible to arrive at this figure with increasing accuracy, 

 and the percentages calculated for the more recent years will be 

 correspondingly more accurate. 



Considerations of space preclude details being given in tabular 

 form of the whole of the results obtained for the period of eight 

 growing seasons up to 1917, but the more essential figures are 

 as stated below — 



I. Plantation D. — Japatiese Larch. 



