Tropical Forests 
But at Sierra Leone there is a distinct change in the 
vegetation even towards the summit of Mt. Sugarloaf: 
the high winds and exposure prevent the continual 
moist hot-house heat which is required for its true 
development. But along a great river valley such as the 
Congo, the wet-jungle slightly modified may be continu- 
ous, extending up the tributary rivers and their smal! 
streams just so far as they remain so sunk below the 
general level of the country as to preserve this moisture. 
Even at about 7000 feet in the Wimi valley on Ruwen- 
zori, one is reminded at every turn of the coast jungle 
at Sierra Leone. 
This is not at all surprising, for there is a nearly con- 
tinuous series of hot, moist, forest-clad slopes or steamy 
valleys right across Africa from Ruwenzori to the Congo 
‘mouth, and thence along the shore’ to the Sierra Leone 
peninsula. In the Amazon valley,so far as I] can under- 
stand Dr. Ule’s description, the entire valley and its tribu- 
taries are clothed with essentially the same wet-jungle 
forest up to the eastern slopes of the Andes in Peru.*? 
But in such an aeroplane as has been suggested, one 
would pass sometimes over plateaux, or perhaps over 
slightly undulating ground, with here and there a range 
of mountains rising well above the general level of the 
country. These plateaux will not be covered with the 
true wet-jungle, which begins to fail a little before the 
crest-line of the coast mountains. Most of them will 
be savannahs covered by tall “elephant grass,” or even 
by low steppe-like grasses with a few scattered trees, 
Occasionally the rolling hills and valleys will be “ park- 
like,” or it may be wooded, but the trees are not tall, 
and there is nothing like the rich undergrowth and 
riotous vegetation of the true wet-jungle. Every river 
will usually have its fringe of wood or “ gallery wood.” 
* The inundated forest of the Amazon is different, as one would expect, 
from that which is above the annual floods, 
aty 
