Plant Communities of the World 277 



growth. Well known is the federation Quercion pubescentis, 

 or "Shiblyac" a sub-Mediterranean, submontane scrub widely 

 distributed in Bulgaria, Rumania, and Jugoslavia, and in Italy 

 westward to the Spanish Monte Bajo and eastward to the Cau- 

 casian countries. Dominants are Quercus pubescens, Berberis 

 vulgaris, Viburnum lantana, Syringa vulgaris, Cotinus coggy- 

 gria, and Paliurus austrdis, among others. Similar scrub of oak, 

 Rhus, Fendlera, and Cercocarpus, I have passed in the Wasatch 

 Mountains, as well as near Palmer Lake on the mesa. 



In the Alps, moist siliceous slopes where avalanches discour- 

 age the growth of breakable wood are clad with green-alder 

 scrub (Alnus viridis), sl thicket of very flexible twigs. 



lO.Hiemisilvae: Raingreen forests (monsoon forests). — The 

 dominant trees of these forests shed their foliage in dry hot 

 summers, but burst into leaves with the beginning of a rainy 

 season. Leaves are mosdy small and compound in accordance 

 with the continental tropic climate unfavorable for tree grov^h. 

 Green bark often assists in assimilation. In Africa these rain- 

 green forests — thorn forest, savannah forest, or monsoon forest 

 — cover very large areas from Portuguese West Africa through 

 northern Rhodesia to the Congo, Tanganyika, and North 

 Bechuanaland, as well as on the south side of the Sahara. Many 

 species of Acacia are dominants. They are also frequent in 

 Asia and in South America, as, for example, the catinga and 

 monsoon forest on the dry calcareous hills of Minas Geraes. A 

 Prosopetum juliflorae is conspicuous on the permeable sand and 

 clay soil of the southern shore plains of Jamaica. 



ii.Hiemifruticeta: Raingreen scrub. — Inward on the conti- 

 nents, trees give way to bushes. This scrub fringes the deserts 

 and enters them at edaphically moister points. The association 

 of the screw bean and mesquite (Prosopetum pubescentis) cover 



