196 ON THE DISTRIBUTION OF PLANTS. 
others, th e@ ‘‘ kieselstete ,” were aac to silicious rocks. 
extending t s we see that only few spe- 
cies, if any, are everywhere growing on tive same substratum. 
the neighbourhood of Christiania some a are only found on 
t ces 
local oe counterbalanced deficient in climate; or rather, 
there is in every tract a remarkable difference in the climate of 
its various s looaltics, 
r circumstance which is of very great importance in 
determining the distzibniion is the struggle ven the different 
species themselves. If the climate is fav urable, species may 
Ww 
no peat would form. In the forest tracts of oe Norway there is 
many a weather-beaten hill-top, hundreds of feet below the upper 
limit of trees, and bigs bare of wood from exposure to win 
weather, and from want of vegetable soil. On such hills we some- 
times find alpine plants, which shun the shade ‘of trees. Several - 
Species grow on the mountains on wher re red are constantly 
e og 
fully cultivated under ‘identical conditions ; nay, many plants which 
naturally only grow in yery wet places thrive remarkably well in 
When 
the gardener removes weeds and keeps off competitors, ae show 
themselves much So oe on soil and moisture than in the 
t places where the grea num of flowering 
plants is found are rich in light. In Norway most of the rare 
phenogamous plants grow in the following localities: on slate and 
limestone poor in vegetable soil to be wooded; on the 
friable shales of our mountains agers peat, heather, and lichen will 
ued stow ; on open shores, if the fjord-water is not too fresh; on 
e cliffs, even on the —= eee granite, wie the vegetable 
