SECTION XIII 

 CLASS X. PSILOPHYTES. SAVANNAH-FORMATIONS 



CHAPTER LXXVIII. SAVANNAH-FORMATIONS 



Under the heading of savannah-vegetation we may place a number 

 of tropical and subtropical formations that are paralleled by steppe- 

 formations. Moreover, as the external conditions become more favourable 

 there is a successional series, quite analogous to that shown by steppe- 

 formations, leading from desert and desert-like succulent steppe, through 

 xerophytic bushland and grassland, to semi-mesophytic bushland, which 

 provides a stepping-stone to mesophytic forest. 



The formations belonging to the savannah-type are linked with 

 those of steppe by transitions, and it is not easy to draw a sharp dis- 

 tinction between the two sets, yet the former differ essentially in the 

 larger dimensions of the constituent plants, and above all, in the presence 

 o/ trees. 



We may regard as belonging to savannah-vegetation the following 

 formations : 



1. Thorny savannah-vegetation, including : () orchard-scrub, 

 [b) thorn-bushland and thorn-forest. 



2. True savannah : tropical and subtropical savannah. 



3. Savannah-forest, including bush-forest in Africa and 'campos 

 serrados' in Brazil. 



Appendix. Evergreen tropical bushland : West Indian Croton- 

 bushland. 



CHAPTER LXXIX. THORNY SAVANNAH 



Orchard-scrub. 



Under the name of 'orchard-steppe' Hans Meyer ^ describes a 

 formation that covers many square miles in the Kilimanjaro region of 

 East Africa. It is alhed to desert-like steppe. The soil is bare and 

 only at certain spots shows a slight growth of grass ; shrubs and herbs 

 arelacking, at least in the dry season. Dotted over the surface at intervals 

 of 3 or 4 metres are tolerably regular little trees which are from 2 to 

 4 metres in height. They are richly armed with thorns, and for the most 

 part have ternate or pinnate leaves, but are lealless during the dry season.- 



' Hans Meyer, 1892 ; Volkens, 1897. ' See Pfeil, 1888; Englcr, 1895. 



