264 Groom.—Remarks on the O ecology of Coni ferae. 
by Conifers during that season. Yet despite of this, evergreen Coniferae 
advance into the extremest positions in the cold-temperate region. Although 
Larix sibirica reaches 72°3o'N. as a prostrate shrub, Finns sylvestris and 
Juniperus communis reach 70° N., and J. communis var. nana goes at least 
as far north as 71 0 N. Again, while Larix decidua ascends to an altitude of 
2,400 metres in Switzerland, this limit is equalled in the same country 
by Finns montana and surpassed by Juniperus communis var. nana. Yet 
it is possible that in its tree-form Larix is better capable than any other 
conifer of enduring extreme cold, and we know that Taxodium distichum 
advances into an extreme habitat of another kind, namely swamp. Moss 
(’ 07 ) gives statistics suggesting that in north-temperate types certain 
deciduous species attain higher latitudes and altitudes than do allied ever¬ 
green species. In this connexion it may be pointed out that in the tall 
evergreen humid forests of Burma and the Malabar Province, the majority 
of the tallest trees are deciduous, and tower above the lofty trees which pro¬ 
duce the main roof of the high forest : again, some of the few giant trees 
that are evergreen are only sub-evergreen, as they cast off the old leaves 
with the appearance of the new foliage. Yet in these forests, too, some of 
the tallest trees are evergreen, so that we cannot absolutely say that those 
exposed to the extremest condition are deciduous, though the tendency 
is in this direction. 
There is one clear distinction between coniferous and dicotylous trees, 
namely, in their power of withstanding equal injurious influences that 
suddenly damage the tree. Coniferae succumb more readily, whether the 
injuries be wrought by chemical or cultural agencies, or by animals or 
plants. 
Despite of the wide range of distribution of such species as Juniperus 
communis, Mayr arrives at the conclusion that Conifers are less capable than 
are dicotyledons of acclimatizing themselves. Mayr’s view is probably 
correct, when we limit its scope to the relatively short periods during which 
attempts at acclimatization have been made and to the attempts made 
where the climate is continental. 
In regard to chemical injuries, it is well known that Conifers, less sensitive 
than certain deciduous dicotylous trees to the action of sulphur dioxide, are, 
nevertheless, more easily killed by smoke. The cause here is triple. First, 
the leaves are exposed to the influence of smoke for a longer time ; secondly, 
the aggregate leaf-surface is often larger than in the case of dicotyledons ; 
thirdly, the sulphur dioxide of smoke kills leaves that required several 
years for their production. 
In connexion with the last cause, it may be noted that complete defolia¬ 
tion, especially if repeated once or twice, of an evergreen conifer by insects, 
fungi, or other agencies, leads to the death or at least serious weakening 
of the tree ; whereas a deciduous dicotylous tree may suffer defoliation 
