xxix BEACH AND RIVER-DRIFT 433 



there sterile and but a summer annual, the seed-vessels, it is argued, 

 must have been brought by the currents from the south. 



The reference to Cakile maritima as a summer annual on the 

 north coast of Norway is of interest ; but I may point out that it 

 displays a similar behaviour in England on the north coast of 

 Devonshire. Here, during the latter half of July, 1903, I found the 

 fruits common in the stranded drift, and often in a germinating 

 condition, whilst numerous seedlings one to two inches high with 

 the fruit-shell still attached were growing out of the sand. From 

 this arises the curious reflection that an annual which germinates 

 in the end of July could scarcely be expected to mature its fruit 

 before the winter. It would seem that this beach plant hampers its 

 own dispersal by its misdirected efforts ; and the idea suggests 

 itself that we have here the explanation of its sterility in the north 

 of Norway. Had it been a perennial like Arenaria peploides and 

 Lathyrus maritimus it might have had a similar distribution within 

 the Arctic Circle. 



Quite other considerations seem to be suggested by the 

 perennials Crithmum maritimum and Euphorbia paralias. In 

 these cases, although the seeds or fruits, as the case may be, will 

 float for months in sea-water without apparently sustaining any 

 injury, the species are confined to the warmer parts of the European 

 region. 



From Convolvulus soldanella we obtain another story. Its 

 occurrence in the temperate regions of both the northern and 

 southern hemispheres, great as the floating powers of the seeds 

 may be, is concerned with something more than with questions 

 relating to modes of dispersal. The circumstance that in its 

 distribution in the temperate regions it is practically coterminous 

 with Ipomea pes caprae in the tropics is very significant (see 

 Note 49). 



Each one of the English beach plants with buoyant seeds and 

 fruits has its own story of the past to tell. Time has indeed 

 gathered on our beaches current-dispersed plants, which, if they 

 could speak, would tell us strange stories of many latitudes, stories 

 of change within the Arctic Circle, and stories of great events 

 within the temperate regions, and, as in the case of Convolvulus 

 soldanella, stories of a past within the tropical zone. It cannot be 

 said that investigators lack clues leading to lines of inquiry into the 

 age that immediately precedes our own. 



Yet valuable as our British plants would be for this purpose, 

 they do not afford any indication that currents have played an 

 VOL. II F F 



