326 C. F. M. SWYNNERTON. 



following the same general direction as that river. The surface soil is a coarse, 

 loose, whitish sand, and numerous vleis, still wet in the dry season, indicate the 

 presence below of the usual impermeable layer. 



The basalt 'plains (PL x, fig. 2) adjoin the granite-gneiss on its south. They cross 

 the Buzi and cover a great extent of country to the south of it. The ground, reddish 

 where the rock is exposed, browner or blacker in the interleaved alluvial patches, 

 dries rapidly after the rains and shrinks and gapes. In the country actually 

 investigated by me it is possible that the Buzi, flowing between fairly high banks, 

 determines the height of the water-table. 



The sediinentary area — or rather the area where this stratum is continuously exposed, 

 for it underlies both the basalt and the dolerite — fills the great oblong tract enclosed 

 between the Mtshanedzi and Buzi rivers (see Map). A broad strip of the same 

 formation runs thence up the Buzi to the British border. It is hilly throughout, 

 the soils are mostly compact, and the rock frequently outcrops. Except in the strip 

 just referred to, it is not well supplied with permanent streams. 



The suh-ofhitic dolerite, as dyke or cap, dominates largely between the Mtshanedzi 

 and the Lusitu, and especially at and south of Spungabera in Gwenzi's country. 

 It is accompanied by a red, rather clayey, yet well drained and highly fertile, typical 

 " trap " soil, and abounds in excellent permanent streams. 



The Sitatongas themselves are of quartzite, flanked by schists, trap, etc. ; 

 apparently (Thiele and Wilson) the schists dominate to the north of them, in the 

 area traversed by my native expedition. 



Distribution of Woodland Types. 



The granite-gneiss carries open (mixed) Bracliystegia bush usually of a rather 

 poor type (PI. xiv, fig. 2). Its vleis are nearly bare of wooding, except for the 

 fine trees on the ant-heaps that stud both vleis and dry land. The finer vleis in 

 particular are lined by a short green sedge (Fuirena). The male tsetses are found 

 in rather special connection with this. 



The basalt, as might be expected from the above description, tends to carry a very 

 poor type of bushy (PL x, fig. 2), mixed, but commonly more or less stunted and 

 very open woods — the " lowland bush savannah " of my classification (p. 320). Thorn 

 groves occur in places ; elsewhere, on exposed or nearly exposed sedimentary 

 rock, Brachystegia patches. The grass, short in some places, is long in others. 

 Fires are earlier here than anywhere else. 



The sedimentary rock of the "Oblong" and its northward extension carries 

 itondo {Brachystegia-Uapaca forest) of a particularly fine type, with a good deal 

 of sapling undergrowth and, in places, patches of invading primary shrub formation 

 (v. p. 320 and the figures there referred to). The mutongoro {Uapaca sansiharica) 

 often forms close groves beside vleis. The grass growth is seldom dense or very high, 

 except in open places (PL xiii, fig. 1), but great and annoying burr areas, of four 

 semi -herbaceous species of Triumfetta (dzunzu), occur. They dry up and are leafless 

 in the winter. 



The dolerite carries (a) wooding of the dense mixed secondary types, largely 

 composed of highly deciduous species, and including Bavhinia thickets ; (6) open 



