204 WEST AFRICAN FORESTS AND FORESTRY 



nobilis, Berlinia Heudelotii, Baphia nitida, Chlorophora excelsa, Cola 

 laurifolia, Parinarium subcordatum, Kigelia ^thiopica, Uaptaca Guineensis 

 (here a large tree and sometimes prop-rooted), Ficus spp. Smaller 

 trees and shrubs are : Spathodea campanulata, Voacanga obtusa and V. 

 Africana, Morinda citrifolia, Xylopia j^CLfviflora, Zanthoxylum Sene- 

 galense, Oncoba spinosa, Vangueria euonymoides, Ixora radiata, Poly- 

 sphceria macrostyla, Garcinia ovalifolia, Myrianthus serratus, Elceis 

 Guineensis and Raphia vinifera. Not all of these extend far beyond 

 the Benue, but the majority of them will be found in one or other 

 fringing belt far into the deciduous region, and perhaps the two which 

 best represent this extension of the semi-evergreen to the savannah 

 are the woody climber Alchornea cordata and the tree Irvingia Smithii. 



In a general view, Northern Nigeria, thus lying beyond the equatorial 

 belt, possesses plant features which, apart from river and stream fringes, 

 range between the mixed deciduous and xerophilus habit, and in the 

 dry season the prevailing character of the open savannah forests is 

 a monotonous drab or grey, intersected by the dark lines of greenery 

 following the streams or encircling the swamps. The climate is largely 

 of the continental type, with a temperature ranging from 120° F. to 40° 

 or less (exclusive of thermometer readings on the Bauchi plateau), and 

 a rainfall which throughout will usually fall between 30 and 50 or 60 

 inches, with diminution to 20 or even 10 inches in the most northerly 

 provinces. Such a climate, with the concomitant regularity of two, 

 not four, well marked seasons, the dry and the wet, is entirely that 

 associated with the occurrence of savannah formations, scattered bush 

 with prevailing grasses, suffrutescent herbs and small trees, much open 

 grass or thinly timbered park-land, with stretches of thick woods 

 which are generally not heavily grassed and never cumbered with 

 impenetrable undergrowth. 



Trees which are valuable timber species in the moist southern 

 forests often scarcely attain reputable dimensions in the deciduous 

 zone. 



These conditions also, which are doubtless partly the result of ill- 

 considered human operations, put certain definite restrictions on 

 cultivated species and determine the character of the natural products 

 of the wild. The staple cereal is Dawa or Sorghum, instead of maize, 

 with Gero or Pennisetum typhoideum in the North. Possibly the limit 

 of Guinea Corn as a staple of native cultivation is also the limit of 

 the savannah forests, i.e. of the region of trees of secondary size, short 

 of the region of Acacias, of Geza, Combretum altum, and of scrub, 

 where Bulrush Millet is the commoner. Both species are generally 

 cultivated along with beans, Vigna Sinensis. The sweet potato displaces 

 the yam and cassava ; industrial cultivation is represented by cotton 

 and indigo. Of forest products, the most representative are Shea nuts 

 and gum arabic, rather than rubber and large timber ; and lastly, both 



