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 

 of trees. 



We may regard as belonging to savannah-vegetation the following 

 formations : 



1. Thorny savannah- vegetation, including : (a) 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 allied to desert-like steppe. The soil is bare and 

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

 are lacking, 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 leafless during the dry season. 2 



1 Hans Meyer, 1 892 ; Volkens, 1897. ' See Pfeil, 1888 ; Engler, 1895. 



