SOUTH WESTERN PARTS OF EUROPE. 47 



favorable climate. However some grasses and 

 mosses are exceptions to this rule. 



2. Many species, which are smooth in the North 

 of Europe, prove hairy in the South, as Teucrium 

 Scordium, Lotus corniculatus, &c. A similar phe- 

 nomenon is observed in alpine plants, and in the 

 vegetables of the highest northern latitudes. In- 

 tense cold and intese heat in this instance produce 

 similar effects. 



3. Many plants, perennial in northern, arc 

 annual in southern regions. The heat and drought 

 cf the latter cause the roots to die away. I alfo 

 find that many annual plants from the South of 

 Spain and Portugal easily become perennial when 

 kept in green-houses ; but on the contrary, I know 

 of no instance in which a plant, indigenous both to 

 northern and southern regions, is annual in the 

 former and perennial in the latter. Ricinus is often 

 adduced as a case in point, but this is not a native 

 of the North, and its extraordinary rapid growth 

 seems to be the cause of its exception from the 

 general rule. Salicornia herbacea is no exception, 

 as it is found together with S. fruticosa. 



