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THE WATER RELATIONS OF THE PINE (PINUS PINASTER) 
AND THE SILVER TREE (LEUCADENDRON ARGENTEUM).* 
By R. D. Aitken, M.Sc. 
(Union Government Kesearch Scholar). 
Communicated by Prof. D. Thoday. 
(With one Text-figure.) 
I. Introduction. 
In two papers recently published in the 1 Proceedings of the Royal 
Society,' Farmer (1) has given an account of experiments he has performed 
with a view to ascertaining, among other matters, whether " the efficiency 
of the wood can be usefully expressed in a quantitative form, and to what 
extent separate species differ." As a result of his experiments he concludes 
that the efficiency of the wood can be thus expressed, and describes a 
method of measuring it, and defines the " specific conductivity " of the 
wood as " the quantity of water transmitted through 1 sq. cm. of wood, 
15 cm. long, in 15 minutes under a pressure of 30 cm. of mercury." 
The clearest result of his experiments is that evergreens possess wood of 
markedly lower efficiency than that of the broad-leaved deciduous trees, and 
that the absolute range of variation in individual species is far narrower 
than in deciduous forms. A few examples from the tables in his papers will 
illustrate this : 
Evergreen. Deciduous. 
Name. Spec. cond. Name. Spec. cond. 
Scots pine . . . 13 ± 2 . Common oak . . . 75 ± 15 
Euonymus japonica . 121 . Euonymus europaeus . 40 2 
He further suggests that the xerophytic character of many of the ever- 
greens may be due to the low conductivity of their wood, and says, " It 
becomes intelligible why a plant apparently xerophytic may yet be restricted 
to localities in which it is never really subject to drought. The wood is 
* The cost of this research was in part defrayed from a Union Government 
Research Grant. — D. T. 
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