186 COLONIAL REPORTS MISCELLANEOUS. 



very long periods at a stretch ; but they rapidly dry up at the 

 end of the rains, and the soil is then thoroughly turned over by the 

 action of the earth-worms. Literally hundreds of thousands of 

 the latter must operate within the space of a few acres, for the 

 surface of the soil is often for many square miles in succession 

 absolutely covered with their castings. These, when dry and 

 hard, render the act of walking over them a very fatiguing 

 operation. 



In such areas an impermeable pan of hard clay or sometimes of 

 laterite rocks exists close to the surface of the soil and renders the 

 latter swampy. 



Another feature of the savannah forests is the annual prevalence 

 in them, early in the dry season, of fierce grass fires that do an 

 incalculable amount of harm to tree growth and keep it in check. 

 The fires are generally most intense and destructive on the dried- 

 up swampy areas which are, as a rule, covered with tall, coarse 

 grasses belonging to the family Panicece. 



A high proportion of the trees possess a very strongly developed 

 protective layer of bark on their stems and branches, and this is 

 not unfrequently accompanied by a corresponding increase in the 

 thickness of their root system ; in fact the latter is sometimes 

 monstrous in its development. These appear to be contrivances 

 to guard the trees against damage from the fires, as well as adapta- 

 tions to a xerophytic climate. 



The average height of the tree vegetation is much less than that 

 characteristic of the monsoon, rain, and fringing forests, but 

 occasionally gigantic specimens of the Odoum (Chlorophora 

 excelsa), the silk cotton tree (Eriodendron anfractuosuni), and the 

 baobab (Adansonia digitatd) are to be met with in the savannah 

 forests. 



The vegetation of the latter is very characteristic, and is 

 enumerated below : 



The AnonacecR are represented by 



The wild custard apple (Anuna senegalensis}, a woody 

 shrub. 

 The Papaveracece by 



Argemone mexicana; a weed. 

 The CapparidacecK by 

 A species of Capparis. 

 Cleoine ciliata ) m . , 



Gynandropsis pentaphylla \ Tr P lcal weeds - 

 The Bixineoe by 



Cochlospermum tinctorium; a characteristic shrub of this 

 formation. 

 The Hypericinece by 



Species of Psorospermnm ; shrubs and trees. 

 The Malvacece by- 

 Various species of Sida, Urena, and Hibiscus. They are 

 all weeds yielding good fibres. A species of the last genus 

 (H. lunarifolius) is the best fibre-yielding plant amongst 

 them, and is sometimes cultivated by the natives. 



