216 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



It seems to me, therefore, that the boundaries of the larger 

 floras, the limits of the petty invasions and skirmishings which 

 we see in the flower-world round Glasgow, and the range of any- 

 particular species, are all very much of the same nature. 

 They are very rarely definite : there is a border or debatable 

 land. To study them properly, a purely artificial system is 

 perhaps best. Any attempt to make geological boundaries 

 applicable to, say, the Potamogetons or the Chenopodiums, would 

 06 absurd. The only convenient system generally applicable is, 

 in fact, latitude and longitude, as has been, to my mind, most 

 conclusively shown by Mr. C. B. Clarke.^ 



1 Biologic Regions, Phil. Trans. Roy, Soc. London, Vol. CLXXXIII. 

 (1892), p. 371. 



