200 WEST AFRICAN FORESTS AND FORESTRY 



The Goriba or Dum Palm, HypJicene Thebaica, is predominant, 

 accompanied also by the Giginya or Deleb Palm, while the Date begins 

 to appear. 



Within the limits of the Soudan Zone of vegetation many different 

 types of savannah may be found, besides the expected alterations in 

 botanical groupings resulting from the presence of perennial moisture 

 or due to elevation and rocky outcrop. Leaving the latter out of 

 account, a few notes may be made of some of the varieties familiar to 

 travellers in the Northern Provinces. 



1. Tree Savannah or Savannah Forest. 



Across a considerable area of Central Hausaland, e.g. occupying 

 a large part of the Zaria plateau west of the Bauchi Highlands, 

 the country, where not cleared for farming, is covered with an open 

 deciduous forest of fair height. This is a fairly closely wooded type, 

 and although it contains few truly evergreen elements apart from 

 those lining the streams, there is, perhaps owing to differing vegeta- 

 tive periods for different species and to the double flowering season 

 noted for many trees in West Africa, practically always a fair 

 amount of foliage present. A proportion of the trees have well 

 developed stems and fairly high crowns, with a leafy canopy which 

 filters but never excludes direct sunlight, and the average height of 

 the larger trees is from 30 to 40 feet. In the best developed 

 portions of such forest the grasses do not predominate, but frequent 

 clearings or patches of stony outcrop lead to the open conditions 

 in which hardy perennial grasses take root, and annual burning 

 results in the encroachment and multiplication of areas of the 

 lower bush savannah referred to below. 



This variety of forest is typically seen in Zaria province, e.g. 

 between the village of Ruka and the Koriga stream, near which point 

 a sudden drop in elevation occurs, and is familiar in parts of South 

 Sokoto, Kontagora and Nassarawa, etc. Lophira alata has its chief 

 habitat here, but perhaps the prevailing and most characteristic tree 

 is one called Doka, which has been identified as Isoberlinia doTca, 

 Craib, et Stapf . It has broad, shining leaves, and large, flat 5-6 seeded 

 pods which dehisce with curling valves. It seeds abundantly, and young 

 seedlings spring up quickly in the forest or by wayside clearings, etc. 

 Along with it will be found its congener, the Fara doka, Isoberlinia 

 Dalzielii, Craib, et Stapf., less abundant, and differing as to its more 

 obvious features in having leaves not shining, a paler grej^ bark and a 

 general slight degree of pubescence of all parts. Both species exude 

 a coarse red resin, which does not appear to be of value. 



Most of the arborescent species mentioned in the list of the average 

 association detailed above are to be found, sometimes harbouring 



