242 ON TRAPA NATANS. 
ce that Trapa n 
cessation of its cultiv 
would probably vanish quickly, almost as soon as its cultivation was 
stopped. e variety of this plant, which now grows in Scania in one 
h 
unfavourable influence (comp. Areschoug, ‘* Om den Europeiska 
in the north-east of Scania go against the view of its extermination 
in other localities of the Scandinavian peninsula by the influence of 
physical conditions. This seeming contradiction can be solved in two 
different ways—either the plant has not in Immeln had to struggle for 
its existence against so dangerous rivals as in other localities whence 
it has disappeared, or some circumstances especially favourable to the 
plant have in that locality been able to, in some way, neutralise the 
unfavourable physical conditions. 
The Trapa natans which grew in Sweden in the last century was 
not quite identical with the form now living in the middle and south 
of Europe, and was described by Wahlenberg (Fl. Suecica, i., p. 100) 
