208 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 
Limits to the Range of Plant-Species. 
By G. F. Scorr Extiot, M.A., B.Sc., F.LS., F.R.G.S. 
[Read 30th August, 1898.] 
W3EN 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; 
Tragopogon pratensis, 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 LXXIL,, p. 277. 
