CiiAi. IJ CHARACTERS OF Tlir: TllMPICRATK CLIMATIC 427 



Africa; finally, numerous Rhamnaccac, particularly belonging to the genera 

 Rhamnus (Europe, North Asia, North America), Phylica (South Africa), 

 Ceanothus (California). The mainly tropical Vitaceae are mostly repre- 

 sented as lianes, but also by aberrant forms in the warm temperate bells. 

 \^itis vinifcra is indigenous in Mediterranean countries, most other species 

 of Vitis in North America. 



Tricoccae: the Euphorbiaceae are not so important in temperate as in 

 tropical floras ; yet some of their species, specially those of the genus 

 Euphorbia, are very widespread in the most diverse formations. Buxus 

 sempervirens (Mediterranean countries, Atlantic Europe, temperate Asia) 

 and Empetrum nigrum (north temperate and polar zones) are the commonest 

 representatives of the Buxaceae and Empetraceae. 



The TItyinclaciiiac (Thymelaeaceae, Penaeaceae, Proteaceae) are by a vast 

 majority mcsotherniic. but the most of them are confined to the warmer 

 belts. Their chief centre is in the dry districts of South Africa and 

 Australia. 



UiubcUiflorac: the Umbelliferae are almost exclusively mesothermic and 

 form a chief constituent of the flora of the north and south temperate 

 zones, specially in grassland formations (Fig. 237). Drude shows that of 

 the three sub-families into which he has divided the Umbelliferae. the 

 Hydrocot}-loidcae are austral, the Saniculoideae both austral and boreal, 

 the Apioideae boreal as regards most genera. The Araliaceae are for the 

 most part megathermic, but }-ct are richly represented in the warmer 

 districts outside the tropics. ICurope possesses only one species, Hedera 

 Helix. The small family Cornaceae is almost exclusi\ely north temperate. 



Of the Saxifragiuac the Crassulaceae are chiefly inhabitants of dr\- hot 

 districts and are strongly developed in South Africa. The but slightly 

 homogeneous Saxifragaceae are represented in both temperate zones hy 

 dissimilar groups of forms, as are also the Hamamelidaceae. A few allied 

 families (Cunoniaceae, Bruniaceae, Pittosporaceae) are indigenous chiefly in 

 the southern zone. 



Rosiflorae: the Rosaceae are almost exclusively mesothermic and form 

 an Important component of the north temperate flora ; the south 

 temperate zone possesses only a few genera, which arc however in some 

 instances rich in species (Acaena in South America, Cliffortia in South 

 Africa). Roseae, Prunoideae, and Pomoideae are boreal. 



Of the three families of Lfguiniiiosae, the Papilionaceae are by far the 

 most important in the temperate zones ; within which they arc richly 

 represented in the most widely different formations. The Mimosaceae 

 arc limited to the warm temperate belts and are extremely important in 

 xerophilous woodland, speciall}- in South Africa, Australia (Acacia), and 

 Argentina (Mimosa). Only a few Caesalpiniaceae overstep the tropics 

 (Cercis, Ceratonia Siliqua, Gleditschia). 



