TYPES OF VEGETATION 23 



great mass of cold, heavy air, and from these was liberated 

 an outward-blowing wind which carried over the Southern 

 plains the finer particles of soil and vegetable fragments 

 that had accumulated on the surface of the ice. These 

 steppes are amazingly fertile. The soil is black with 

 humus, and cultivation can be carried on year after year 

 with little or no manuring. Clover in some places grows 

 to a height of 15 feet and hemp to 20. Such a soil is 

 very retentive of moistiu-e, and this is important in a 

 region where the rainfall is so scanty. Towards the 

 South and the East the fibrous black earth dies away 

 and the steppes pass into dry barren pastures. 



5. The Mediterranean Region. — This has a subtropical 

 climate characterized by wet cool winters and dry warm 

 suimners. In summer cultivation is limited by drought 

 and in many places is possible only if the soil is irrigated. 

 The winters are so mild that there is no break in the 

 vegetation, and most of the crops that we grow in summer 

 can be grown there in winter. Trees are not abundant. 

 Most of the forests have been cut down and are now 

 represented only by their undergrowth of shrubs, the 

 maqui, and there is much grass. Deciduous trees are 

 rare except in dainp spots, while the chestnut is restricted 

 to mountainous tracts, where, of course, the climate is 

 different. The characteristic vegetation is evergreen, 

 e.g., the olive, orange, oleander, evergreen oak, arbutus, 

 bay-tree, yew, cypress, stone-pine, and myrtle. Aro- 

 matic plants are common. One palm, Chamcerops 

 humilis, reaches Europe, where it occurs on the Riviera. 

 The flora of the Mediterranean has changed within his- 

 torical times. When the Greeks landed in Southern 

 Italy, forests of oak and beech were common; now they 

 are rare, the beech being confined to the highest moun- 

 tains. This is largely ovidng to the gradual dessication of 

 the whole Mediterranean region, which has been going 

 on for ages. But man has accelerated Nature by replacing 

 the deciduous trees which he cut down by evergreens, 

 most of which are derived from Asia and suit the climate 

 better. The orange was brought from the East during 

 the Middle Ages, and since the discovery of America, 

 the magnoha, agave, and Indian fig have been introduced 

 from the New World. This shows how important human 

 control is in considering present-day floras. 



