1887-88.] Annual Increase in Girth of Trees. 



255 



Tilia europcea. 



No. 2 is the handsome spreading lime, which stands quite 

 free from neighbours in the centre of the Botanic Garden ; 

 No. 18, a healthy-looking young tree at the north end of the 

 west shelter belt ; and 21*, a large, handsome, well-clothed 

 tree, grouped with two or three others near the lawn at 

 Craigiehall. The foliage in all three has always appeared 

 quite healthy, except occasionally when insect-eaten, a mis- 

 fortune to which this species seems peculiarly liable. 



Average Anmml Eate of Increase. — Notwithstanding the 

 good appearance of these trees, their annual growth has been 

 singularly slow, averaging only 0-27, the best of them 

 averaging 0-35 and the worst 017. That this low rate is 

 quite abnormal there can be no doubt, and in fact the 

 average in 1878 was 0'47, or removing 21*, the increase 

 of which was much depressed even in 1878, the remaining 

 two averaged 0'60 in that year. In the case of No. 2 our 

 information extends unusually far back, as Sir Eobert 

 Christison has preserved notes of its girth in 1860 and 1874. 

 The following are the general results : — Girth at 3 feet up 

 in March 1860 = 67-50 ; November 1874 = 75-50 ; November 

 1887 = 80-50. This gives an increase of 8 inches in the first 

 fifteen years and of 5 inches in the last thirteen years, or an 

 annual rate of 0-53 for the first period, and of 0-38 for the 

 second. But if we take the last five years of the latter 

 period, the rate was only 0-24. This shows a rapidly 

 diminishing rate from 0-53 to 0-24, the average for the whole 

 twenty-eight years being 0-46. It is pretty clear, then, that 

 this tree, notwithstanding its flourishing appearance, has 

 passed its prime, and this would appear to indicate that even 

 healthy limes, with every advantage of position, cannot be 



