222 KNUT F^GRI 



accidental diaspores was reached during the latter part of the nineteenth cen- 

 tury with gravel ballast. Many plants, which were then more or less regularly 

 imported to Scandinavia and were considered at least transient members of 

 the flora, are now rarely seen, or not seen at all except as old herbarium 

 specimens, and might perhaps just as well be omitted from future handbooks 

 of the flora. Similarly, the recent habit of many mills to grind or grit also the 

 sorted-oiit weed seeds before selling them for fodder deprives the avid 

 collector of many interesting (but insignificant) finds. 



Nevertheless, there are still many sources of introduction left even today : 

 packing material, wool rejects, etc. Most of the plants introduced this way 

 either (1) are already represented in our flora, or (2) cannot estabUsh them- 

 selves; but sometimes an immigrant secures a foothold. Buuias orient alls or 

 Matricaria matricarioides may be quoted among the classical examples, the 

 immigration of which dates back, respectively 200 and 100 years (Holmboe, 

 1900). And from today Epilobium adenocaulon may be mentioned, which 

 evidently has spread very rapidly since World War II, although it had been 

 found in Scandinavia before that time. 



With anthropochorous dispersal being overwhelmingly important in 

 our days, one is likely to overlook the contemporaneous "natural" long- 

 distance dispersal. It is very difficult to decide if man has had nothing to do 

 with the case — most of the cases in which man's activity can be ruled out, are 

 undateable. The case of Coleantlms subtilis is one of those that can probably 

 be comparatively well dated (Lid, 1948). Unfortunately, the plant failed to 

 establish itself. Another most probably recent and non-anthropogeneous 

 (Holmboe, 1930) case is that of Elisma natans (Luronium natans). The plants 

 that introduce themselves by natural means are generally more successful 

 immigrants than the anthropogeneous ones, within which group the percen- 

 tage of failures is very great. Unsuccessful immigrants of the former group are 

 usually not observed, but there is no reason to believe that they do not occur, 

 cf. the Mucuna seeds found on our shores. It is of importance that the two 

 cases mentioned above presume modern, spontaneous, long-distance dispersal 

 of the magnitude of at least some 300-400 and 1000 km. Other instances of 

 spontaneous, long-distance diaspore transport readily come to mind. Although 

 one cannot exclude the possibility that disjunct finds may represent relict 

 occurrences, many of them also must represent long-distance dispersal, not 

 only where the dispersal mode is more or less evident (sea transport, waders, 

 ducks, etc.), but also in plants with a less obvious dispersal ecology. 



One may discuss how far back the "modern" era of dispersal should stretch. 

 The great discoveries of the fifteenth and sixteenth centuries seem to furnish 

 a good delimitation. Before that time whatever transport there was, was 

 confined to the relatively small area of the Medieval World. The increasing 

 intensity of traffic could not bring anything new to Scandinavia that had not 

 had a chance of immigration hundreds of years before. 



