THE CONTINENTAL FLORA OF SOUTH SWEDEN 325 



17. The distribution of Silene viscosa on the Baltic shores 



me to occur in another quarter, viz. in the mode of dispersal of the species. 

 As Sernander (1901 b, p. 403) has pointed out, the waves may be an effec- 

 tive vehicle and, perhaps, also the water-currents are to be counted in. To 

 this, probably, may be added a dispersal of the seeds by birds; the striking 

 agreement of the distribution area with migratory bird-routes can hardly be an 

 accident. The frequency of the species in its localities being very changeable 

 (often the species is a real accident) the dispersal must be, in any case, a very 

 effective one, but in the same time, strongly restricted to certain regions. 



The distribution of Isatis tinctoria on the Baltic shores, where it may be a 

 real native (cf. Hjelt, »Conspcctus» Vol. iii, Pars ii, p. 390), shows a note- 

 worthy coincidence with that of Silene viscosa: it is rather abundantly spread on 

 the seashores of South-East Sweden and South-West Finland but lias only a few 

 occurrences in other shores (cf later on p. 372). 



The Swedish distribution-area of Potentilla riipeslris (Fig. 18), the peculiarity 

 of which has already been mentioned (p. 307), is strongly i.solated. Its nearest 



