RAINFALL 11 
winds favouring transpiration are frequent. We find, how- 
ever, that even where these latter unfavourable conditions 
are absent in the district of small rainfall, as in sheltered 
ravines or dens, hepatics are still scarce. It must be added 
that the rock formation in which these dens occur is in 
general less retentive of moisture than in the dens in the 
wetter district of the west coast, and therefore less suitable 
for hepatics, and probably also with less humidity; but 
even with similar rock character in the two sides of the 
country the scarcity of hepatics in the dens of the drier 
districts is striking. The deficiency in the number of 
species in the drier districts is not so noticeable as the 
general scarcity of hepatics. Prolonged search over a 
considerable tract of a dry district will result in the 
discovery of nearly as many species as in a wet district, 
leaving out of account the peculiar Atlantic species of the 
western side of the country, but there can be no comparison 
between the amount of hepatic vegetation present in each. 
A larger number of plants will probably be seen in a single 
day’s ramble in a wet district than would be found during 
a year’s searching over a much larger area of a dry 
district. 
Lists of species made under different amounts of our 
average rainfall have not resulted in much matter of 
interest, but some general features may be given. There 
are about 145 species which have been found on the low 
ground, and of these, 93 have also been found, among other 
places, in the district under 30 in. Of the 145 species 
there should be excluded 23 Atlantic species of the west 
coast, and of the 93 there should be excluded 11 peat-moss 
species, as the latter being on permanently wet ground 
have a wide distribution independently of the annual rain- 
fall; Also from the 145 species may be excluded four 
which have only been found in shady ravines, when in the 
drier districts, as the humidity must be considerably above 
the average. There are thus 82 species out of 118 which 
have been found in the drier districts, and a few of these 
are local and rare, but this applies to both factors. Taking 
into consideration the comparatively small area which 
there is under the 30 in., we see that the actual number 
of species in Scotland is not much affected by the rainfall. 
