SOUTH WESTERN PARTS OF EUROPE. 63 



The deep vallies of Traz-os-montes, for instance 

 the valley of the Douro, are distinguished by the 

 production of Spanish plants. 



The mountains along the Douro as well as the 

 Cape Estrella, are naked and dry. The)- produce 

 some plants of Northern Europe, as Scleranthus 

 annuus, Achillea Millefolium, &c. with some few 

 belonging to middle Spain, and several that are 

 exclusively their own. 



The Estrella is not so well watered nor so shady 

 as the Gerez. On its higher regions we find, in- 

 deed, birch and mountain-ash, but, upon the whole, 

 fewer plants of the North of Europe than on the 

 Gerez. The under wood consists of Erica arborea, 

 and australis, with some Cytisi. Their naked sum- 

 mits and rocky parts produce several plants belong- 

 ing to the South of France, but none belonging to 

 the North of Europe. From this it appears, that 

 it is the want of shade which principally prevents 

 the extending of these plants. 



The heaths of Middle Portugal are covered with 

 Pinus maritima Gerard. The most common 

 Cisti upon them are C. Chciranthoides, C. sambu- 



