FLORA OF EAST AND MIDDLE AFRICA 43 



ward almost to the shores of the Albert Nyanza and the 

 Bahr-el-Jebel Nile. 



Much of the tree vegetation which is characteristic of 

 this zone occurs also on the border of the forested regions 

 rising above it. The quaint straggling Croton elliottianus, 

 the African yew, Podocarpus gracilior, the olive, and Albizzia 

 fastigata are trees of this sort. A very characteristic tree 

 or small shrub is the gray sagebush-like camphor-bush, 

 Tarconanthus camphoratus, which covers large areas in the 

 Rift Valley, Loita Plains, and North Kenia districts. Asso- 

 ciated with this are Carissa bushes, trees of Acocanthera 

 ahyssinica from the wood of which the deadly arrow poison 

 is derived, a small, slender tree, Dodonea viscosa, and sev- 

 eral species of the oak-like Combretum trees. From the 

 nyika we have as stragglers both of the giant euphorbias 

 and several tree acacias which are wide-spread in the zone 

 and give it a characteristic African appearance. Kigelia 

 ethiopica with its pendulent sausage-like fruits is a com- 

 mon tree in the Nile watershed. 



The grassy plains which are the characteristic plant 

 feature of the zone are covered by a heavy black cotton soil 

 in marked contrast to the red soil of the hill and forested 

 areas bordering them. During the rainy season a luxuriant 

 growth of grasses a few feet in height covers the plains, but 

 gradually it is grazed down by the great herds of game 

 until only mere stubble is left in the dry season. The most 

 extensive grass plains included in this area are the Athi, 

 Kapiti, Loita, Laikipia, Naivasha, Uasin Gishu, and the 

 whole eastern Nyanza lake steppe. 



A characteristic bush of this region is the gall-covered 

 Acacia fistula which forms a scattered growth over much 



