816 



Acacia horrida. (L.) Willd. (Mimosaceae ) 39355. Seeds 

 of the doornboom or thorntree of South Africa, presented by 

 Mr. J. Burtt-Davy, Agricultural Supply Association. "A 

 glabrous flat-topped tree, usually spreading more than its 

 height. The most widely distributed of all South African 

 trees, extending from Capetown through the Karroo to 

 Damaraland , Orange River Colony, Transvaal, Natal, and 

 Delagoa Bay. Its range is however curiously affected In 

 places, being absent, possibly through frost, in several 

 large flat alluvial localities where single trees have 

 grown to perfection. It ascends to about 4000 feet alti- 

 tude from the eastern coast and considerably further from 

 the western, but is absent from the higher parts of the 

 Drakenburg, and seldom mixes with Proteaceae, thus indica- 

 ting that soil as well as climate controls its distribu- 

 tion. Occasionally it forms a fine spreading tree 30-40 

 feet in height, and with stem 2 feet in diameter, much 

 more frequently it is a small umbrella-shaped tree of 10 

 to 15 feet in height with a clear bole only to 6 or 8 

 feet, and the constant regrowth dots or covers the veld 

 with all smaller sizes in suitable localities where it is 

 not kept down. Although usually evergreen, yet in dry 

 cold carroid localities it is often leafless for a con- 

 siderable part of the year, and in some localities it is 

 continuously leafless for years in succession, and is then 

 enormously spiny and colors the veld white instead of 

 green. In most places its use is principally for fuel, 

 for which purpose there is no better wood: but as this 

 does not, except near the towns, use up all that grows, 

 its increase in remote localities is a difficult matter to 

 check. Fire burns the grass under mature thorn-trees 

 without doing them much damage, and as the seeds germinate 

 most readily after being soaked in boiling water or half 

 roasted, those grass fires aid rather than retard re- 

 growth. Chopping off trees at the ground only induces 

 an abundant coppice growth, but it is found that by chop- 

 ping them off two feet above ground during summer, the 

 coppice growth is more easily controlled, and the stump 

 of ten dies. Native locations usually become free of thorn- 

 tree eventually, partly through the unrestricted native 

 demand for fuel, kraalwood, etc., and partly through the 

 browsing of goats, which of all artificial methods is the 

 surest means of keeping the tree down. A small brown 

 scale-insect, however, (Prosopophora prosopidis , var. mimosac) 

 is found to kill the trees wholesale on the occasions of 

 its visits in the Bedford district. During very dry win- 

 ters it is not an uncommon practice to fell a few leafy 

 thorn-trees daily as a green bite for stock; during summer 

 the shade of the spreading tree is sought after by cattle 

 and sheep; young plants are always browsed, and when ob- 



