144 TRANSACTIONS OF THE [ Sess. LXXv. 
Consequently, on the low grounds, after the surface of a 
marsh has been raised sufficiently above the water-table 
for meadow to develop in a region of hotter and drier 
summers, the sedges continue to dominate until peat moor 
and heath plants appear. On drier ground again the 
natural vegetation is also heath or moor. We have seen 
that there may be a certain development of grassland 
on the links and by the seaside generally, which, though 
encouraged by grazing, is probably of natural origin. But 
with this exception practically all the pastures owe their 
existence to human influence. Specifically the following 
are the main factors involved in the production of grass- 
land out of the natural formations :— 
Heather-burning; grazing, treading, and manuring by 
domestic cattle; drainage; cultivation; spread of grass 
seeds from cultivated land and other grassland. 
Without in the meantime attempting to classify them, I 
shall enumerate the chief situations where, through natural 
or artificial causes, the grasses dominate. 
The Stations. 
Stream sides—For a short distance on either side of a 
stream that overflows its banks occasionally there is the 
requisite moisture for the formation of a meadow, and, 
owing to the draining influence of the channel of the 
stream, there is no stagnation and consequent souring of 
the soil. A narrow strip of meadow may thus be formed, 
but further from the stream sedges dominate. 
Small islets in the lochs.—In this very limited type of 
locality somewhat similar conditions hold and_ similar 
vegetation results. Manuring by waterfowl and absence 
of grazing aid in encouraging the growth of tall herbs, such 
as Spirea and Angelica. 
Grassy banks.—On sloping sea-cliffs on sheltered coasts 
where there is little salt spray, and on similar inland slopes, 
of which there are few, the perfect drainage permits a 
grassy formation, as a rule, though not always, to oust the 
heath. 
Moist grass slope.—Strips of green may sometimes be 
seen running down a hillside, which exhibit on closer 
