IOO 
R, H. Compton. 
XEROPHILY IN THE CONIFERS AND MICROPHYLLY. 
HE xerophilous structure of the leaves of the Coniferae has 
attracted much attention from the point of view of their 
ecological relationships. Since the leaf-structure is markedly 
xerophilous in respect of thickened cuticle, sunken stomata, etc., 
it has been customary to regard the whole tree or shrub bearing 
these leaves as a “ xerophyte.” The difficulty that has been found 
in correlating this structure with the occurrence of Conifers in 
situations in which apparently an abundant supply of water is 
available, has led to the tentative assumption that xerophily in 
these cases is a character fixed by heredity. For instance, 
Schimper, 1 speaking of the needles of the Larch, suggested that the 
slight relic in them of xerophilous structure must be regarded as 
hereditary, and of a character opposed to their present conditions 
of existence. Miss Stopes 2 also suggested that the xerophilous 
character of Conifer-leaves is due to the hereditary tracheidal 
structure of the wood, and the consequent limitation of the rate of 
flow of the water current. Professor Groom, 3 however, shewed 
that this explanation breaks down in the case of the Larch with its 
rapid transpiration current. 
It is true that the assumption of the hereditary fixity of a 
character to explain apparent lack of adaptation may become 
merely an easy method of disguising ignorance of the real 
physiological relationships between a plant and its environment: 
this seems to be the case, to a certain extent, in the somewhat 
similar instance of “swamp xerophytes,” where hereditary xerophily 
has been assumed by some authors. It is necessary in such cases 
to produce independent evidence of hereditary fixity, evidence 
unrelated to the supposed incompatibility of structure and habitat. 
Let us therefore consider the Coniferae from this point of view, 
with the object of discovering whether a strong hereditary factor 
enters into their powers of adaptation, and if so what may be its 
nature. 
There is much disagreement as to the ecological adaptation of 
Conifers to their environment. On the one hand the assertion is 
1 Plant Geography (Engl, edition), p. 565, 1903. 
2 “The ‘ Xerophytic ’ Character of the Gymnosperms.” New 
Phyt., VI., p. 46, 1907. 
3 “ Remarks on the Oecology of Coniferae.” Ann. Bot., XXIV., 
p.241,1910. 
