25-i Dr Christison on the [sess. lii. 



Quercus Cerris. — Of two trees under observation, one is in 

 the east shelter belt of the Botanic Garden, surrounded by 

 shrubs, but not pressed on by neighbouring trees ; the other 

 stands quite freely on grass at Craigiehall. Both are hand- 

 some trees, and have always been quite healthy in appear- 

 ance. 



The average annual rate of increase is three-quarters of an 

 inch, but No. 10*, the larger of the two, furnishes much the 

 greater share of this, its average being nearly an inch, while 

 that of Xo. 43 is only a little above half an inch. In favourable 

 circumstances this seems to be a fast-growing species, even 

 at a considerable age. No. 10* being close upon 7 feet in 

 girth, and still maintaining a growth of nearly an inch a 

 year. It appears also to be hardier than the native oak. 



The range in the trees separately has not been great. The 

 extremes in No. 43 were 0-65 and 0-35, and in No. 10*, 

 which was only measured for eight years, 1'25 and 0'70. 

 The aggregate range also was inconsideraljle. 



This species appears to have suffered little in the first 

 period of depression. There was no visible bad effect. No. 

 43 fell off in its increase only in 1880, and not severely. 

 No. 10* was not measured till that year, but as far as the 

 data go appears to have followed much the same course as 

 tlie other. Both completely and permanently rallied in 

 1881. They did not suffer at all in the subsequent de- 

 pressions. 



Qurrcns rulra. — The single specimen of the American 

 oak under olxservation is a young tree, standing freely in the 

 Botanic Garden. A good many of the twigs are dead, and it 

 lias rather a shabby look. 



The annual rate of increase was 0"4r), probably abnormally 

 low, owing to the defective condition just described; its 

 anmuil range has been slight, and during the three consecu- 

 tive bad years the girth-increase suffered materially only in 

 1880, a complete rally taking place in the third of them. It 

 was in 1880, h(jw(;ver, that tlu; damaged conditicm of the 

 twigs was first noticed. Hius, allJiougli there were unmis- 

 takable visible signs of injury from the severe season of 

 1880, there was no corresponding effect on the girth-increase. 

 In the f)ther seasons of depression the yield of this tree was 

 above its average. 



