242 
Groom.—Remarks on the Oecology of Coniferae. 
2. The occurrence of Coniferae in evergreen tropical humid regions. 1 
3. The demand on the part of certain cold-temperate Coniferae for 
a relatively humid habitat. 1 
I propose, therefore, to discuss several points in connexion with the 
coniferous mechanism in relation to water. 
(a) The Coniferous Mechanism does not necessarily involve 
a Slow Rate of Transpiration per Unit Surface of Leaf, 
NOR XEROPHYTIC STRUCTURE IN THE LEAF. 
Though the xerophytic structure of the evergreen Conifer leaf is 
associated with a slow rate of transpiration, the deciduous larch-leaf 
transpires rapidly. This is shown by results obtained by Von Hohnel 
(’80). 
The subjoined statistics record the number of grammes of water 
transpired per gramme air-dry weight of leaf-substance during the period 
April 1 to September 31, 1879. (Von Hohnel’s results have been con¬ 
verted into approximate numbers.) 
Sorbus torminalis 
Larix decidua 
Tilia gran difolia 
Fagus sylvatica 
Betula alba 
Elm 
Quercus Robur 
Acer platanoides 
Picea excelsa ... 
Pinus sylvestris 
Pinus Laricio ... 
Abies pectin at a 
L75° s 
M5° 
1,030 
-Deciduous 
«45 
755 
660 
520/ 
2IO| 
io 5 1 
100 
Evergreen 
751 
But these results do not necessarily imply all they seem to, as 
misconception will arise if Von Hohnel’s method of calculation and mode of 
experiment are not taken into account. 
This will be clear, so far as the method of calculation is concerned, 
from the following example. If we suppose that there are two flat leaves, 
say a sun-leaf and a shade-leaf of the same species and of equal surface, 
and that the former leaf weighs twice as much as the latter; then, if the 
sun-leaf under the influence of direct sunlight is transpiring twice as much 
water in a given time as the shade-leaf in weak diffused light, the rate 
of transpiration will nevertheless seem to be the same in the two leaves 
if we estimate according to Von Hohnel’s method, that is, per gramme dry 
1 Compare Schimper, 1898. English Version, pp. 564-5. 
