238 ZONES AND REGIONS [Pt. Ill, Sect. I 



sented in the first place by the Passifloraceae, Begoniaceae, and Flacour- 

 tiaceae, also by the Loasaceae (America), Samydaceae, Turneraceae, 

 Caricaceae, some of the species of which are common and prominent. 



The Myrtiflorae consist exclusively of megathermic species in the 

 Melastomaceae, Combretaceae, and Rhizophoraceae, of which those of the 

 first family play a prominent part, especially in America, as fine blossoming 

 shrubs and herbs, whilst to the last two the majority of shrubs and trees 

 of the mangroves x belong. Neither the Oenotheraceae nor the Lythraceae 

 are absent. 



Of the Rosiflorac, the Chrysobalaneae are exclusively megathermic, 

 whilst the other groups of Rosaceae consist almost exclusively of meso- 

 thermic plants and therefore within the tropics occur only on mountains. 



The three families of the Lcgnminosae, the Mimosaceae, Caesalpiniaceae 

 and Papilionaceae, belong to the most important groups of forms of the 

 tropical flora. They include trees, shrubs, and herbs, that frequently climb 

 and are equally important in humid and dry districts, in woodland and 

 in grassland ; many are remarkable for their fine flowers. 



The different families grouped together tentatively as Hysterophyta are 

 pre-eminently megathermic, and include many of the most unique products 

 of the tropical flora, especially among the Aristolochiaceae, Rafflesiaceae, 

 and Balanophoraceae. 



The Ericinac are with few exceptions mesothermic, and therefore quite 

 unimportant in the true tropical flora. They however show numerous 

 species in the mountain flora — Vaccineae, Rhododendron. 



Among the Primulinae the Myrsinaceae are exclusively tropical, whereas 

 the Plumbaginaceae include only a small number of megathermic species, 

 and the few Primulaceae are alpine plants. 



The families of the Diospyrinae — Ebenaceae, Diospyraceae, Sapotaceae — 

 consist almost exclusively of tropical woody plants. Several of the 

 Sapotaceae are commonly cultivated. 



Among the Contortae, the Loganiaceae, Apocynaceae, and Ascle- 

 piadaceae are represented in many species of the most diverse forms of 

 growth, whilst the Oleaceae and Gentianaceae, as mesothermic families, 

 occur only as mountain plants. 



The Tubiflorae possess many megathermic species among the Convol- 

 vulaceae, and in the Boraginaceae the tribe of the Cordieae, characterized 

 by stone-fruits, is purely tropical. 



The most important tropical family of the Pcrsonatac is that of Solanaceae, 

 to which very numerous herbs and shrubs and some small trees belong. 

 The pre-eminently megathermic families Bignoniaceae, Gesneraceae, and 

 Acanthaceae have numerous representatives, and the Lentibulariaceae 



1 See Chap. VI of this section. 



