10 THE DISTRIBUTION OF HEPATICA IN SCOTLAND 
drier and exposed districts, as transpiration is excessive, 
the only one which can be considered at all frequent in 
such a habitat being the xerophytie Frullania dilatata. 
The opposite condition is seen in the shady ravines of the 
West Highland coast-line, where the moist atmosphere and 
comparatively small amount of light hinder transpiration ; 
here we find hepatics in quantity on the stems of trees as 
well as on rocks, ete. In moist soils the most important 
division is into those which are peaty and those which 
are not. 
The geological formation of the rocks, except in the case 
of limestone, is almost a negligible factor, further than 
whether they form a soil retentive of moisture or not. 
The sandstone and voleanic rock districts, except granite, 
are nearly always poor in species, even in the most favour- 
able climatic districts, while in schistose rock districts there 
are usually species in plenty. A few species are more 
frequent when there is some lime in the soil, but no species 
is contined to this soil in Scotland, unless it be in the case 
of Metzgeria pubescens and Lophozia turbinata. Also a 
few species, as Nardia scalaris, are rare on limestone. 
Two rare species, Marsupella sparsifolia and Sphenolobus 
Pearsoni, have only been found with us on granite, and 
Chandonanthus setiformis is much more common when on 
this formation. As with habitats so it is with geological 
formations; in our moist insular climate, so favourable for 
the growth of hepaties, species do not limit themselves to 
a particular kind of rock as they appear frequently to do 
in countries less favourable for these plants. 
RAINFALL 
As the distribution of hepatics is largely a question of 
climate, the amount of rainfall has an important bearing 
on the subject. We find in Scotland that hepatics are 
scarce in all districts which have less than an average of 
30 in. of rain annually. These districts form a narrow 
border along the east coast from Caithness to Berwick. 
Here also there is in general little shelter, but strong dry 
