V. INEQUALITIES OF DISTRIBUTION. 433 



Europe, and continued into Asia. The area of Erica 

 cinerea, the frequent associate of the Calluna throughout 

 Britain, is more contracted in Europe ; stopping far short 

 of Asia. The area of Erica ciliaris is still more con- 

 tracted ; heing only a comparatively small portion of 

 south-western Europe, namely, Britain (including Ire- 

 land ?), western France, Spain with Portugal. The area 

 of Erica umbeUata is again smaller ; being a portion of 

 the Spanish peninsula only. 



In addition, it is to be kept in recollection, that the 

 geographical position of the areas, relatively to each 

 othei', is quite as varied as their dimensions. The 

 smaller areas of some species may be wholly included 

 within the larger areas of other species, and in different 

 situations within them. The areas of some species are 

 situate wholly or partially more northward, more south- 

 ward, more eastward, more westward, higher or lower, 

 than the areas of other species ; being either quite sepa- 

 rated and apart, or else intruding one upon another in 

 the most varied modes and degrees. Some species range 

 along the shores or near the coasts onty ; while others 

 are quite inland ; and others occupy both situations. 

 Moreover, the continuity of distribution may be inter- 

 rupted more or less within the area, regarded as a whole 

 space. And great inequalities of profuseness or rarity 

 may exist between species, although the extent of their 

 geographic areas, and even their continuity of distribu- 

 tion may not very widely differ. In short, the often-cited 

 simile of rain- drops on a pool of water, — the circles of 

 which cross and interfere with each other almost infi- 

 nitely as they widen, — might be applied to the areas of 

 plants, as it has been to so many other things. 



This enumeration of inequalities and diversities would 

 read like an idle repetition of trite truisms, were there 



VOL. IV. 8 K 



