308 FORESTRY IN THE CROWN COLONIES. 



to a more temperate climate. The seasons are well defined. The 

 dry season lasts in the south from November to March, and the 

 rainy season occupies the other 7 months ; in the north the latter 

 is reduced to about 5 months. During the dry season the 

 " Harmattan " blows, a north-easterly wind which brings with 

 it from the Sahara a thick haze composed of minute particles of 

 dust. During the harmattan the nights and early mornings are 

 cold, but the days are very hot. 



The Temperature varies, according to situation and elevation, 

 as follows : — 



Minimum from 45 to 70 degrees. 



Maximum from 93 to 117 degrees. 



Mean annual from 72 to 84 degrees. 

 Rainfall. — The approach of the monsoon or " rainy season " is 

 inaugurated by numerous tornadoes. In the south the wind then 

 blows from the south-west bringing a heavy rainfall to the country 

 near the coast, which gradually decreases on proceeding inland. 

 In the Niger delta the fall varies between 100 and 150 inches. 

 Then comes a belt with a fall between 75 and 100 inches, which, 

 near the northern edge of Lower Nigeria is reduced to below 

 75 inches. The rainfall of Northern Nigeria does not exceed 

 about 56 inches, and on the northern edge as little as 16 inches 

 have been recorded. 



2. Main Types of Forest Growth. 



The character of the different types of Nigerian forest is, apart 

 from elevation, mainly determined by the amount of water at the 

 disposal of the plants. They are : — 



(a) The Mangrove Swamp Forest is confined to the tidal areas 

 of the rivers and lagoons, between high and low water 

 mark. The forest practically consists of Rhizophora 

 racemosa, Rh. mangle and Avicennia africana. 



(6) The Freshwater Swamp Forests occur chiefly in the vicinity 

 of the larger rivers, and they are often due to their 

 overflow ; they occur also in the deeper valleys of the 

 hills. Important species are Lophira procera (the Red 

 Iron Wood), Mitragyne macrophylla, also Raphia vinifera 

 (the Bamboo Palm), and Calamus Barteri. The red iron 

 wood is considered the most durable timber on the West 



