GENERAL NOTES ON THE FLORA 9 
of a different nature from that of a floristie work such 
as this. 
Comparatively few species in Scotland are confined to 
any particular habitat. This especially applies to the High- 
lands, where the humid conditions are so favourable for 
their existence, that we find them on different situations, 
such as on both rocks and trees, which in a less favourable 
country would be limited to one or the other of these 
positions. Ina large part of the south of Scotland, and 
towards the east coast, the climate is drier, and various 
species are more limited to special habitats, as appears also 
to be the case on the Continent. The presence or absence 
of continual moisture is the ruling factor. A few species 
grow almost equally well under either condition, but the 
very great majority do not. To a few species dry soil or 
dry rock is necessary, but the prevalence of hepatics in any 
part of our country depends on there being a considerable 
amount of moisture. When withdrawn to any great extent, 
hepatics disappear. This is well seen in a district favour- 
able for hepatics, as in the West Highlands, where species 
will be found in quantity in the natural woods, but when 
the woods are thinned the species decrease, their place 
being taken by mosses, in which group there are more 
xerophytes. Hepatics cannot withstand competition with 
mosses except in the most humid parts of woods. We see 
on tree stems and rocks on which the former have first 
taken hold, that a moss, as Hurhynchium myosuroides, 
perhaps follows, and the hepatics are choked. The effect of 
drainage is almost entirely to destroy the hepatic vegetation, 
except in the case of those which manage to find a suitable 
habitat at the moist side of the drain. They are scarce in 
the region of cultivation, this region being in large measure 
one of small rainfall and absence of shade, and likewise 
scarce in those districts of the subalpine region where the 
rock seldom appears on the surface, as over almost the 
whole of the upland parts of the Lowlands. They are 
generally plentiful over the whole of the uncultivated 
regions of the Highlands, where the rainfall is large, but 
are in small quantity usually on the south and west sides 
of hills, and plentiful on the north and east sides, this being 
a matter of moisture. Species are scarce on trees in the 
