890 Dr Christison on the [sess. lih. 



Observations on the Annual Increase in Girth of Trees in the 

 Boyal Botanic Ga.rden, and at Craigiehall, near Edin- 

 hurgh, from 1878 to 1887. Part II. By David 

 Christison, M.D., F.S.A. Scot. 



(Read 14th February 1889.) 



The Second Part of this paper gives, under several heads, 

 the general conclusions which may be drawn from the facts 

 recorded in the First Part. 



1. Annual Rate of Girth Increase in different Species 

 of Trees. 



In determining by measurement the comparative rate of 

 growth in trees, or different species of trees, we must take 

 into account various considerations which may affect the 

 fairness of comparison, even when the trees are situated in 

 the same locality and are planted in the same soil. Thus 

 the rate may -be influenced by depth of soil, degree of shelter, 

 freedom from overcrowding or the reverse, and by the age of 

 the trees concerned. The last consideration is a perplexing 

 one, as it seems probable that there is a natural rise followed 

 by decline in girth-increase, the limits of which in different 

 species have not been, perhaps cannot be, determined ; and 

 it is certain that a great decline takes place long before any 

 sign of decay is visible in old trees. 



In the following Table I have selected the quickest 

 growers as being on the whole the fairest exponents of the 

 capacity of soil and climate to maintain the growth of the 

 different species. In the statement the species which proved 

 quite unreliable are not included, and the rates are given 

 roughly, so as to show their amount in a general and simple 

 way. On account of the disturbing causes described in the 

 Introduction to the First Part, the general estimates may be 

 too low. I have allowed a little, however, for them, in some 

 cases in which it seemed justifiable to do so. The age of 

 the trees being unknown, their approximate size is given 

 instead. 



It appears from the talkie tliat the Hungary oak has gone 

 far ahead of all the other deciduous species in rapidity of 

 growth, having averaged in fact upwards of li inch during 



