GEOGRAPHIC DISTRIBUTION OF ANGIOSPERMS 269 



(Diapensiaceae), an Australian family (Epacridaceae), and a 

 great massing of heath-forms in the Cape region. 



PEIMULALES. The three families are very distinct in their 

 geographic distribution, Myrsinaceae being tropical, especially 

 American, Primulaceae north temperate and boreal, and 

 Plumbagmaceae characteristically oriental in the halophytic 

 conditions of the Mediterranean and Caspian regions. 



EBEXALES. The alliance is almost exclusively tropical, and 

 in both hemispheres. 



GEXTIAXALES. The alliance as a whole is more largely 

 massed in the tropics through the tropical display of its largest 

 families, Apocynaceae and Asclepiadaceae. It contains also a 

 great liana group (Loganiaceae) characteristic of South Amer- 

 ica and Asia, and there is a pairing of Africa and Asia by 

 the Salvadoraceae. The Gentianaceae have almost a world- 

 wide distribution, but are notable in their numerous alpine 

 species. 



TUBIFLOEALES. This great series is in the main broken 

 up into fairly well-restricted areas, and the chief features of 

 their distribution may be stated as follows : The Labiatae are 

 world-wide in their distribution, being notably massed in the 

 Mediterranean region. The Borraginaceae and Scrophularia- 

 ceae are the great north temperate families. The Solanaceae 

 are everywhere in the tropics, extending into temperate regions 

 especially in America. The Convolvulaceae, Polemoniaceae, 

 and Hydrophyllaceae are characteristically American, the first 

 being chiefly tropical, and the other two characteristic of west- 

 ern Xorth America. The Gesneraceae belong to all regions 

 of the southern hemisphere ; while the Yerbenaceae, Xolana- 

 ceae, and Acanthaceae are notably in tropical South America. 

 There are also two Mediterranean families, the Orobanchaceae 

 and Globulariaceae. The pairing of South America and Asia 

 is shown in the display of Yerbenaceae and Acanthaceae; and 

 of tropical Asia and Africa in the display of Pedaliaceae. 



PLAXTAGIXALES. The genus Plantago is cosmopolitan. 



RUBIALES. The Rubiaceae are prominently tropical Amer- 

 ican ; the Caprifoliaceae and Valerianaceae are north temper- 

 ate throughout both hemispheres : while the Dipsaceae seem 

 to be confined to the temperate regions of the eastern hemi- 

 sphere. 



