22 ON FARLETON FELL 
one-time swamps—such as the alkali deserts of Utah 
—harbour only a limited number of species specially 
adapted to their arduous conditions of life. The same 
difficulty, it may be noted, produces the peculiar and 
specialized flora of the salt-marshes which fringe the 
broad bay on which we look down from Farleton 
Fell. Here there is indeed a superabundance of 
water, but it is so charged with salt that if even the 
most vigorous species of the fields or woodlands are 
transplanted into it they will soon be dead; only plants 
long inured can grow there. Still, the conditions are 
not so adverse but that a continuous mat of vegeta- 
tion extends, growing patchy and dying out only 
where the surface slopes below high-water mark. 
There we enter a new domain, where another race of 
plants, so long inured to salt water that they now 
cannot exist without it, holds possession. 
Thus from absolute deserts, such as the floor of the 
deep sea or the regions surrounding the Poles, we 
pass to semi-deserts where plants are dotted thinly 
over the surface, and thence by degrees to closed 
vegetation of various types, where the plants elbow 
each other over the whole surface as they do in the 
grasslands spread around Farleton Fell, in the woods 
which adjoin them, and on the brown hillsides out to 
the north. But before we pass to the consideration 
of the conditions where favourable environment re- 
sults in a closed vegetation, we may suggest for con- 
sideration the following point of view: that for any 
plant, or group of plants with similar requirements, 
much of the world is a desert—that is, a place where 
conditions are such that it cannot live. For each 
plant there exists, owing to long usage and slow 
