274 



Dr Christison on the 



b 



the summer of 1879, and again in autumn of 1887, and as the 

 age of these trees is known, we are enabled to compare their 

 rate of increase in that period with the rate for the earlier 

 part of their career. 



The great differences in the rate of upward growth shown in 

 the Table admit of some explanation. Thus No. 41 has made 

 no appreciable gain in height in the last eight years, and is no 

 higher now than two others not half its own a^e ; but then 

 the perfect freedom allowed to it all lound has caused the 

 branches to spread outwards rapidly, as w^e have ascertained 

 by actual measurement, and thus the deficiency of growth in 

 one dii'ection is compensated by a rapid increase in another. 

 Again, the slow upward growth of No. 42 in the last eight 

 years corresponds with a marked decrease in the girth- 

 increase, and both are no doubt due to the effects of the 

 hard winter of 1879. The slow upward growtli of No. 48, 

 evidently a very healthy tree, and wliich made the largest 

 girth-increase of all, was probably due to overshadowing and 

 overcrowding. It was cleared of neighliours in spring 1886, 

 and it will be interesting to note the effect. 



The iiulividvMl range was highest in No. 42, 0'50 to 0"05, 

 and lowest in No. 49, 0'55 to 0'30. The aggregate, range lay 

 between 2-90 in 1884 and 1-40 in 1887. From the depress- 

 ing effect of 1879 tln-ee of the six yews, measured in that 

 year, escaped. Five in seven suffered in 1880, and three 

 in seven in 1881. The species participated only slightly 

 in the depression of 1883, so disastrous to some of the 

 evergi-een species; but in 1887 it sulfcred most severely, 

 five of the seven trees reaching their absolute minimum of 

 increase. 



