268 
Groom.—Remarks on the Oecology of Coniferae. 
Summary. 
1. The northern evergreen Coniferae are architectural xerophytes in 
which the extensive surface exposed by the evergreen leaves as a whole 
renders it necessary for the individual leaves to be xeromorphic in form 
and xerophytic in structure. This type of structure enables these Coniferae 
to live in regions where there is a season of physiological drought, in 
situations varying from dry dunes to moist forests, and from arctic and 
alpine situations to tropical sites. 
2 . The tracheidal structure of the wood of these conifers is well suited 
to their xerophytic evergreen leaves ; and a similar type of wood is apt to 
occur in north-temperate and austral-temperate dicotyledons that have 
evergreen xerophytic leaves, as is shown by American species of Quercus , 
Trochodendron , and Drimys. The tracheidal structure of the wood is not 
a bar to progress and to the adoption of the deciduous habit, for in the 
larch a rapid transpiration current flows through it and the leaves transpire 
rapidly. The tracheidal structure of the wood more probably provides the 
conifer with a safety mechanism that is a defence against extinction. 
3. Conifers are more easily deranged and killed by sudden injuries, 
and are attacked by a larger number of serious fungal and insect foes, than 
are dicotylous trees. To their greater vulnerability and smaller powers 
of repairing injuries we may at least partially attribute the defeat and 
extinction of many Conifers in past ages. 
In conclusion I beg to express my thanks, first to Lt.-Col. Prain, F.R.S., 
Director of the Royal Botanic Gardens, Kew, for permitting me to perform 
the physiological experiments at the Jodrell Laboratory, and for some of 
the material used in this investigation; and secondly, to Messrs. James 
Veitch & Sons for twigs of Tetracentron. 
LITERATURE. 
Cannon ( J 05 ): On the Water-conducting system of some Desert Plants. Botanical Gazette, 
xxxix, pp. 397-408. 
Ewart (’ 06 ) : The Ascent of Water in Trees. Phil. Trans. Royal Soc. B., p. 52. 
Gradmann, R. (’ 00 ) : Das Pflanzenleben der Schwabischen Alb. Tubingen, 2. Aufl., Theil i, p. 327. 
Groom, Percy (’ 92 ): On the Thorns of Randia dumetorum. Annals of Botany, vi, p. 375. 
Hohnel, F. von (’ 79 ): Ueber die Transpirationsgrossen der forstlichen Holzgewachse. Mittheil. 
aus dem forstl. Versuchswesen Oesterreichs, Bd. ii, Heft i, p. 47. 
- (’ 80 ): Weitere Untersuchungen iiber die Transpirationsgrossen der forstlichen 
Holzgewachse. Jbid., Bd. ii, Heft iii. 
