60 CHRISTISON—ADDITIONAL OBSERVATIONS ON 
1899 was 221. The subsequent very low rate for seven years to 
1906 of 81 is unaccountable, as the tree seems well-clothed and 
healthy. 
4ESCULUS HIPPOCASTANUM. No. 4. 
Always in the west border. Girthed 123 inches in 1892 and 
for four years had a rate of 31 mil. In 1896, after pruning, the 
increase fell to 191 ; and the average, by a steady decline for three 
years, to 13; and for the next four, to 10. The results for the 
remaining four years to 1906 were even worse, the figures being 
5, 3, 34,0. There is nothing in the appearance of the tree to 
account for this remarkable history, and the removal of surround- 
trees and bushes seems too slight a reason for so great a decline 
in the increase. 
ALNUS GLULTINOSA. No. 7. 
On its original site in the west border. Girthed 8} inches in 
1892 and increased for four years at the rate of 19} mil. In 
1896, after pruning, the increase fell to 72 and the average for 
four years to 44. In the next five it improved to 9, but in 1905 
the increase was only 31, and in 1906 21; yet the tree does not 
seem unhealthy. 
BETULA ALBA. No. 17. 
Always near the north-east corner of the Arboretum shelter belt. 
Girthed 134 inches in 1892 and had the high rate of 41 mil. for 
four years. After pruning in 1896 the increase was only 123, 
and the rate for four years to 1899 was only 104. In 1g00 it 
jumped up to 28, but the rate fell again for six years till 1896 
to 22, not much above half of that before the pruning. 
CRATAEGUS OXYACANTHA. Noit. 
In its original site at the north-west corner of the Arboretum 
shelter belt. Girthed 10 inches in 1892. Dividing the years of 
observation into three periods of four years each and one of three 
years, the first gives a rate of 254 before pruning; the second, 
6$ after it; the third, a recovery to 174; and the last to 24, or 
nearly the rate before the tree was pruned. 
