154 WEST AFRICAN FORESTS AND FORESTRY 
Mahogany is represented in this zone as another species which does not 
attain a greater girth than 10 feet and which is often gnarled and 
crooked owing to the annual grass fires. A medium sized Cedrela, 
or hard cigar-box wood, is found in isolated patches in the northern 
part of the Abeokuta and southern part of the Oyo province. The 
balsam-copaiba-tree is also very common in this zone in the North 
Benin, Onitsha and Ogoja provinces. 
The forests of this zone are perhaps the least valuable from the 
financial point of view, chiefly owing to their geographical position and 
defective means of transport, but economically they are of great value to 
the agricultural community, both for their forest produce as well as their 
soil-preserving and rainfall-conserving properties. The chief timber areas 
are situated in the heavy rain forest and mixed deciduous forest areas, 
though a few have recently been taken up in the mangrove swamps. 
As a minor, though important, development: to the main forests 
are the evergreen hill forests, which find wide development in the 
northern part of the Jebu-ode, Ondo, Benin, Ogoja and Calabar pro- 
vinces. On the whole, the species do not vary so much as might be 
expected, and in many cases it simply means a further distribution 
of certain evergreen trees beyond their zone of natural development, 
owing to suitable climatic conditions in these hills. For instance, 
the red ironwood appears next the mangrove swamp on the bank of 
the St. Barbara River, again in the evergreen forests near Calabar, 
and reappears in the hill forests of Oban, much further north. Probably 
the most typical trees of the hill forests are an unidentified species 
of gum-copal, as well as several species of Guttiferz. 
The fringing forests are found chiefly on the banks of the rivers in 
an area which is otherwise covered with the open deciduous or dry- 
zone formation. Two leguminous trees are most typical of this 
zone. Stray deciduous or evergreen trees from the other zones are 
also seen. Such forest is thick with a fair amount of undergrowth, 
and the trees form a close canopy. The fringes vary from a few 
yards to half a mile in width. 
A further subsidiary form is found on the summits of the highest 
mountains, such as the Boji Hills, with their stunted satinwood trees, 
shrubs and grass. In some places there is yet another minor formation, 
that of the freshwater swamps. Some typical examples of these are 
found on the banks of the Calabar, Osse and Owenna Rivers. In 
most cases only one, or any how only a few species of trees are found, 
whereas in the major formations several hundred different species appear. 
The growth in these swamp formations, both mangrove and freshwater, 
is on the whole not so large as that of the evergreen forest. Again, 
the evergreen forest does not show such fine development or such 
height of tree as the mixed deciduous forests, though occasionally 
the greatest girth of bole is found in the evergreen forests. 
