146 PHYSIOGNOMY OF PLANTS. 



North of Africa, in Spain, and Portugal. Erica vagans 

 and E. arborea also belong to the two opposite coasts of the 

 Mediterranean : the first is found in North Africa, near 

 Marseilles, in Sicily, Dalmatia, and even in England ; the 

 second in Spain, Italy, Istria, and in the Canaries." (Klotsch 

 on the Geographical Distribution of species of Erica with 

 persistent corollas, MSS.) The common heather, Calluna 

 vulgaris, is a social plant covering large tracts from the 

 mouth of the Scheldt to the western declivity of the Ural. 

 Beyond the Ural, oaks and heaths cease together : both 

 are entirely wanting in the whole of Northern Asia, and 

 throughout Siberia to the shores of the Pacific Ocean. 

 Gmelin (Flora Sibirica, T. iv. p. 129) and Pallas (Flora 

 Rossica, T. i. Pars 2, p. 53) have expressed their astonish- 

 ment at this disappearance of the Calluna vulgaris, a dis- 

 appearance which, on the eastern declivity of the Ural Moun- 

 tains, is even more sudden and decided than might be 

 inferred from the expressions of the last-named great natu- 

 ralist. Pallas says merely : " ultra Uralense jugum sensim 

 deficit, vix in Isetensibus campis rarissime apparet, et ulte- 

 riori Sibirise plane deest." Chamisso, Adolph Erman, and 

 Heinrich Kittlitz, have found Andromedas indeed in Kamt- 

 schatka, and on the North West coast of America, but no 

 Calluna. The accurate knowledge which we now possess of 

 the mean temperature of several parts of Northern Asia, as 

 well as of the distribution of the annual temperature into 

 the different seasons of the year, affords no sort of explana- 

 tion of the cessation of heather to the east of the Ural 

 Mountains. Joseph Hooker, in a note to his Flora Antarc- 



