FLORA OF EAST AND MIDDLE AFRICA 49 



altitudes. Several shrubs and small trees belonging to the 

 Ruhiace(S are also common undergrowths. Great vines, 

 several inches in diameter and many feet in length, form a 

 network in some of the highland forest of the Mau and in 

 parts of Kenia. The rubber-producing Landolphia vines 

 often form a considerable part of this network. 



The upper forest at timber-line is marked by a dense 

 growth of bamboo of a peculiar high-mountain species, 

 Arundinaria alpina. The bamboo forest occupies a zone 

 about a thousand feet in vertical height, ranging from tim- 

 ber-line at ten thousand feet down to nine thousand feet. 

 In this belt it grows to the exclusion of all other trees, the 

 stems usually standing a foot or two apart and so close that 

 it is quite difficult to squeeze through the forest without 

 cutting a path. The only trees which are stragglers in 

 this zone are Podocarpus milanjiana and Olea laurifolia.. 

 On the upper timber-line edge a large tree of the order 

 Rosacece appears, Hagenia anthelmintic a, which is character- 

 istic. Practically no animal life is confined to the bamboo 

 zone, and very few animals live within its borders, owing 

 to the soil supporting no undergrowth. The bamboo forms 

 a desert waste between the life of the forest proper and the 

 alpine regions. A narrow fringe straggles down into the 

 forest along streams to an altitude of seven thousand five 

 hundred feet. 



One of the marked peculiarities of the African timber- 

 line is the absence of dwarfing, which is so characteristic a 

 feature of the tree-growth at high altitudes in our northern 

 climes. The forest-trees grow fewer in numbers at the upper 

 levels in equatorial Africa, but they are no smaller in size. 

 Much of the dwarfing in the north is due no doubt to the 



