296 FLORA OF PORTUGUESE EAST AFRICA. 



capoisc. Grczvia sp., Sculopia ZcyJicri, Apodytcs diniidiata, 

 Ficiis Ktilis, F. capci:sis, F. na'talcnsis, Exccecoria africcnia, 

 etc. 



On the Zambesi and northward, a very large number of 

 species are common to East and West Africa, while on the 

 coast the tropical tidal-mud mangroves are cosmopolitan 

 within that zone. 



It is impossible to estimate what is the total number of 

 species found in the Province, but the outstanding features are 

 the predominance of ligneous vegetation and the wide range of 

 many of the species. In my " Forest Flora of Portuguese 

 East Africa," over 500 species of trees and shrubs are included, 

 and doubtless many are omitted, while in regard to Herbaceous 

 species no complete list has ever l^een attempted. 



Those geographical botanists who have dealt with Southern 

 Africa, generally constitute a floral area embracing eastern 

 tropical Africa; thus, Griesbach's "Soudan Region," Bolus' 

 ** Tropical African Region," and Justus Thode's " Kaffrarian 

 Province " agree in general terms, except that the latter is 

 intended to be the extra-tropical continuation southward of 

 the former. 



Such a general classification is necessary in reviewing Africa 

 as a whole, and the flora of Portuguese East Africa practically 

 all falls within the larger region so designated, but for closer 

 work and with more intimate knowledge such a region is far 

 too large, and requires sub-division. 



To what extent the flora of Portuguese East Africa corres- 

 ponds v/ith or differs from that beyond its boundaries north 

 and north-west I am unable to say, but within itself I would 

 suggest the following regions, all of which overlap more or 

 less and have some species common to all except No. i, but 

 still are sufificientlv distinct to be considered separately. 



I. Tidal-mud Region. 



This extends interruptedly along the coast from Delagoa 

 Bay to beyond the Province northward, and embraces all 

 muddy shores, river-banks and lagoons subject to daily or 

 frequent submersion by tide. This submersion naturally ex- 

 cludes all except such shrubs and trees as have developed a 

 special xerophytic habit, which allows them to select and retain 

 enough fresh water to keep them alive, in the midst of sur- 

 roundings which would drown them or kill them with salt, 

 but for such special adaptation, and, strangely enough, most 

 of them live only within such surroundings. This habit ex- 

 tends to certain representatives of several orders, and includes 

 the following trees, known collectively as mangroves, viz.: — 



Rhizophorere : RJiizophora mucrouata. 

 ,, Bnigujcra gymnorhizo. 



Ceriops CandoUiana. 

 Meliaceae: Carapa molucccnsis (Xylocarpus granatiiin). 

 Combretacese : Lumnitccra raccinosa. 

 Lythraces : Soiuicrafia acida. 



