20 O. B. Miller 



Notes on the Distribution of Species in Natural Forests of the 

 TransJ^eian Conservancy. 



By O. B. Miller, Department of Forests. 



Schimper (p. 160. "Plant Geography") in discussing the 

 differentiation of the Earth's vegetation says : " The type of 

 the flora in so far as it depends on existing factors is dependent 



primarily on heat Heat determines the flora, climatic humidity 



the vegetation.*' 



This general rule well explains hov/ it is that a tree like 

 Trichilia emetica which occurs in tropical Africa cannot, in the 

 Cape Province, exist away from the coast. 



But among our coast trees there are many that extend far 

 inland to what is practically the limit of forest-growth (6,000 

 feet) and these usually find their optimum at altitudes ranging 

 round 3,000 feet. Many coast forests and sheltered bluffs above 

 the sea support real yellowwood (Podocarpus thunbergii). 

 This species is found wherever climatic humidity permits wood- 

 land to exist, from the sea to the tops of the mountain range 

 traversing the Transkei, known variously as the Insizwa, Nungr, 

 Mgano and Matiwane. Thunberg's yellowwood is one of the 

 least exacting of our forest trees as, on the upper mountain slopes, 

 it withstands the rigours of climate so much better than its 

 associates that it forms in many parts almost pure forest. In 

 such places its principal competitor is Olinia cymosa^ a tree whose 

 range seems limited to the mountains. 



Gradually one comes to know roughly what may be expected 

 to occur in a given locality and the presence of certain species, 

 such as white ironwood (Toddalia lanceolata) is taken for 

 granted in every wood in the Transkeian Territories. It grows 

 at sea level and Bews reports it from the uppermost Drakensberg 

 forests. Its almost complete absence from the Mgana Range 

 is therefore a matter of surprise. These mountains run from the 

 Tina River to Lady Kok End on the Kinira River. The 



