FLORA OF EAST AND MIDDLE AFRICA 47 



which cannot again support tree growth, and on this ac- 

 count deforestation in the highlands of East Africa is 

 attended by irreparable devastation. The only highland 

 forests outside of this volcanic area are the isolated patches 

 on the Taita Hills, the Mathew, Ruwenzori, and Usambara 

 Ranges, which are in a gneissic region. 



The forest is made up of a great variety of trees, only a 

 few of which occur universally throughout its area. The yew, 

 Podocarpus milanjiana, and the black olive, Olea laurifolia, 

 are the only trees of this class which can stand the extremes 

 of moisture existing between the moist east and the dry west 

 slopes of the forested mountains. A wide-spread tree of 

 the dry western slope is the Abyssinian juniper, Juniperus 

 procera. A more important distributional factor than the 

 division of the forest into a dry western and a moist eastern 

 section is formed by the altitudinal assemblages of trees we 

 find characteristic of the lower edge of the forest, the inner or 

 true forest and the upper or timber-line edge of the forest. 

 Characteristic of this lower edge of the forest, which fringes 

 the open, grassy plains or continues as long tongues border- 

 ing streams down into the plains country, are the straggly, 

 spidery Croton elliottianus, the Brachylcena (sandalwood), 

 and the acacia-like Albizzia fastigata. A conspicuous tree 

 of the forest edge is Dombeya nairobiensis, which is usually 

 covered by a wealth of white apple-like blossoms. On the 

 moist slopes we have added to these the large-leaved shrubby 

 tree, Macaranga kilimanjarica, the columnar Cusonia spicata, 

 tree-ferns, Lonchitis pubescens, and the peculiar tree-lilies, 

 Draccena. The poison-bush, Acocanthera abyssinica, the 

 gray olive, Olea chrysophylla, the yew, Podocarpus gracilioTy 

 and the widely distributed juniper, Juniperus procera, are all 



