232 PHYSIOGNOMY OP PLANTS. 



gamia, are in those regions buried for several months of each year 

 in winter sleep. Over a large part of the earth, therefore, there 

 could only be developed organic forms capable of supporting either 

 a considerable diminution of heat, or, being without leaves, a long 

 interruption of the vital functions. Thus we see variety and grace 

 of form, mixture of colors, and generally the perpetually youthful 

 energy and vigor of organic life, increase as we approach the tropics. 

 This increase can be denied only by those who have never quitted 

 Europe, or who have neglected the study of physical geography. 

 When, leaving our oak forests, we traverse the Alps or the Pyrenees, 

 and enter Italy or Spain, or when we direct our attention to some of 

 the African shores of the Mediterranean, we might easily be led to 

 draw the erroneous inference that hot countries are marked by the 

 absence of trees. But those who do so, forget that the South of 

 Europe wore a different aspect on the first arrival of Pelasgian or 

 Carthaginian colonies; they forget that an ancient civilization causes 

 the forests to recede more and more, and that the wants and restless 

 activity of large communities of men gradually despoil the face of 

 the earth of the refreshing shades which still rejoice the eye in 

 Northern, and Middle Europe, and which, even more than any his- 

 toric documents, prove the recent date and youthful age of our civil- 

 ization. The great catastrophe which occasioned the formation of 

 the Mediterranean, when the swollen waters of what was previously 

 an immense lake burst through the barriers of the Dardanelles and 

 of the Pillars of Hercules, appears to have stripped the adjacent 

 countries of a large portion of their coating of vegetable mould. 

 The traditions of Samothrace, ( s ) handed down to us by Grecian 

 writers, appear to indicate the recentness of the epoch of the ravages 

 caused by this great change. In all the countries which surround 

 the Mediterranean, and which are characterized by beds of the ter- 

 tiary and cretaceous periods (nummulitic limestone and neocomian 

 rocks), great part of the surface of the earth consists of naked rock. 

 One especial cause of the picturesque beauty of Italian scenery is 

 the contrast thus afforded between the bare rock and the islands, if 

 I may so call them, of luxuriant vegetation scattered over its surface. 

 Wherever the rock is less intersected with fissures, so that it retains 

 water at the surface, and where it is covered with vegetable mould, 



