80 CHRISTISON—ORBSERVATIONS ON 
it to say that the following thirteen additional species attained 
an annual average of an inch to an inch and a half in their best 
consecutive five years :—Acer Pseudoplatanus, Fagus sylvatica, 
Prunus Padus, Populus fastigiata, Tilia europea, Betula alba, 
4sculus Hippocastanum, Fraxinus excelstor, Acer campestris, 
Quercus rubra, Crategus Oxyacantha, Quercus robur, Robinia 
_ Pseudacactia. These are arranged in order, Acer Pseudoplatanus 
at the head with an average of all but an inch and a half, and 
Robinia at the foot with exactly one inch; but it must be remem- 
bered that the comparison is not quite fair, as the ages of the 
trees were very different. 
Species that appear to thrive in the Garden but yield com- 
paratively low rates are Carpinus Betulus, Pyrus communts, 
Pyrus Aucuparta, and Quercus Cerrds. 
I]. MONTHLY RESULTS. 
The trees adopted at various periods for monthly measure- 
ments were selected from those observed annually, and the 
reasons for choosing and abandoning successive sets, already 
given in the Introduction, apply with even greater force now 
than in the First Part of our subject. 
Monthly measurements were commenced tentatively by Sir 
Robert Christison in 1880 upon five deciduous and six evergreen 
trees, but the tape he used was too coarse to yield very reliable 
results. In 1882 I added about thirty-five deciduous examples, 
and took monthly measurements of the whole, in the growing 
season, till 1887. The early results, down to 1882, were included 
in a Paper to the Royal Society of Edinburgh in 1883,* and the 
whole results were communicated to the Botanical Society in 
1887.7 
But the objections, already explained, to observations upon 
old and large trees induced me to abandon this set in 1887 
and take up the fresh set ¢ of about thirty-five young trees, used 
* “Observations on the Annual and Monthly Growth of Wood in Deciduous and 
Evergreen Trees.” By the late Sir Robert Christison, Bart., and Dr. Christison. 
Trans. Royal Society of Edinburgh, 1883, pp. 45, 66. 
+ ‘* On the Monthly Increase in the Girth of Trees at the R. Botanic Garden and at 
Craigiehall, near Edinburgh,” by David Christison, M.D. Trans. Bot. Soc. Ed., 1887. 
t ‘‘ Observations on the Increase in Girth of Young Trees in the Royal Botanic 
Garden, Edinburgh, for five years ending 1891,” by David Christison, M.D., 
President. Trans. Bot. Soc. Ed., 1892, : 
