40 ON THE BOTANICAL GEOGRAPHY OF THE 



two very nearly related species, the one in northern, 

 the other in southern climates. These are often 

 so closely a-kin, that they might be considered 

 as originating from one species, but that they are 

 never found to degenerate the one into the other. 

 An accurate observation of such plants might lead 

 to the discovery of the original effect of climate 

 upon vegetables. I must, however, previously 

 observe, that the limits of extension between these 

 species are never distinctly drawn j but on the 

 contrary, that there are countries which produce 

 both. This again affords a ground for considering 

 both as originally distinct. In the following cata- 

 logue I shall also introduce those that are varieties. 



Saiicornia herbacea and fiuticosa are both found 

 in the South of Europe ; in the parts farthest 

 South, the latter only. 



Agrostis stolonifera does not grow in the most 

 southern parts of Europe, but A. alba does. In 

 the middle region both species are found together. 

 Agrostis hispida does not appear in the most 

 southern parts of Europe, but in its stead a new 

 species, or else A. capillaris. 



