2 o 8 transactions—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
that characteristic of the heather moor. The plants have, as a rule, 
a thick cuticle, reduced leaves, waxy coverings, or other modifications 
which have the effect of reducing the amount of transpiration. 
In comparing the flora of our pine woods with that of similar 
Norwegian woods, one is struck by the great rarity of certain species 
in the former which are quite common in the latter, e.g., 
Cornus suecica, L. Pyrola secunda, L. 
Linnaea borealis, L. Lycopodium annotinum, L. 
Vaccinium uliginosum, L. 
These plants are all found widely enough distributed in Scotland, 
although rare, and all are accessory to our pine woods or to the 
neighbouring heaths. There seems good reason to conclude that 
the destruction of the forests has been the cause of this rarity, and 
their re-institution in Britain will only be through the establishment 
of old woods. 
A similar explanation probably applies to those saprophytic forms, 
like Lathrcea^ Neottia^ Goodyera^ etc., which are so rare in our woods. 
Certain of them, such as Corallorhiza^ which we know to be a wood- 
plant in many regions, we usually find on the heaths, where heather 
supplies the shade and food given elsewhere by trees. In his lecture 
to this Society on “ Rare Plants in the Carse of Cowrie,” Mr. Dow 
mentions that the disappearance of Goody era repens ^ R. Br., from 
a wood in the neighbourhood of Longforgan was co-incident with 
the opening up of the wood by the felling of trees. A similar case 
has come under my own observation in St. Fort wood, where in 1893 
I noted more than twenty plants of Goodycra growing in a deeply 
shaded part, while in 1894, ’95, and ’96, I have been unable to find 
any. That part of the wood has been largely opened up by the 
great storm of the winter of 1893. The same storm was, I have 
heard, the means of restricting the area of Goodyera in woods in the 
neighbourhood of Gattanside, Melrose. 
Although the larch is an important social tree in our valley it is 
not native, and its association presents but little difference from that 
of the pine. 
The Birch, Betula alha^ L.—The birch is interesting to us as 
the tree which attains the highest altitude in Britain (Hooker, 2500 
feet). It is also the tree which extends furthest north in Europe, 
and is, in fact, the only European one which reaches Greenland. But 
in Switzerland the conifers are found at a greater altitude than the 
birch. This is a case comparable to that of the oak and the beech, 
and again it seems to be due to the summer storms of Switzerland 
being unfavourable to the growth of the thin-leaved birch. This is 
the explanation suggested by Wahlenberg (Christ, p. 191). 
