208 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



Limits to the Range of Plant-Species. 

 By G. F. Scott Elliot, M.A., B.Sc, F.L.S., F.R.G.S. 



[Read 30th August, 1898.] 



When one reflects upon the enormous literature of Botany, with 

 its 300 and more journals appearing regularly, it is by no means 

 easy to understand why such questions as the above require 

 special treatment. Yet it is certainly the case that the whole 

 question of distribution and limiting range of plants deserves a 

 thorough investigation. 



The range of a species is probably never definitely and rigorously 

 defined. Along the borders of the country occupied, it is striving 

 to push forth skirmishers into new country, or, in other directions. 

 it may be retreating before species better adapted to existing 

 conditions. It may even be throwing off trial forms and states 

 which may or may not survive. 



For example, one Linaria has, almost within the memory of 

 living botanists, travelled over the railway lines of Great Britain ; 

 Trago20ogon ^;r«<en&'i5, Linn., has advanced within three years 

 along two to three miles of the Caledonian Railway at Lockerbie; 

 Mimulus luteus, Linn., and Elodea canadensis, Michx., are both 

 conspicuous examples of species which have, in the historic period, 

 definitely increased their area. Dr. Lange^ gives a list of 390 

 species which have in the last 200 years settled themselves in 

 Denmark. On the other side, we know too well how fern- 

 collectors and others have devastated well-known localities, and 

 yet modern agriculture is even more disastrous to many of our 

 wild plants. In fact, in such a country as ours, interruption of 

 range is the rule, not the exception. A heaVy gale, or the cutting 



1 Lange, Bot. Central , Band LXXII., p. 277» 



