DISPERSAL AND SURVIVAL OF PLANTS 195 



dispersed by the Gulf Stream from the coast of North America, as late as in 

 Post-glacial and Present time, as far north as Spitsbergen (Love and Love, 

 1947; Hadac, 1960). 



Other shore plants which can fit into a similar distribution pattern, but 

 probably one of an older date, belong to genera such as Cochlearia. Honckenya, 

 Mertensia and Glaux (Ridley, 1930), of which the first three reach the Arctic 

 part of our area, but Glaux so far is found only in Iceland, and not yet in the 

 Faeroes. 



The large size and weight of Honckenya and Cakile seeds (cf. Table 3) 

 indicate that they are well adapted to floating. Those of Glaux are smaller, 

 individually, but usually united in a cluster of five and most likely therefore 

 quite buoyant. Mertensia seeds are lighter in weight, but of a relatively large 

 size and may possibly float well. Cochlearia groenlandica is found as a shore 

 plant throughout our area but it consists of a complex, circumpolar group of 

 subspecies whose areas are not yet well known, and it is somewhat uncertain 

 whether it should actually be included in the group of plants dispersed by 

 sea-currents. 



Salt water plants are of course naturally adapted to dispersal in sea-water, 

 and the genus Zostera produces seeds (with a corky appendage) and vegetative 

 parts which seem to have the necessary buoyancy for long-distance dispersal 

 by sea-currents. In Iceland (Love and Love, 1956) and perhaps also in 

 Greenland (Bocher, Holmen and Jakobsen, 1957; Jorgensen, Sorensen and 

 Westergaard, 1958) the genus is represented by Z. stenophylla, an American 

 species. Whether the Faeroes plants are true Z. marina, as indicated by the 

 Flora of the Faeroes (Rasmussen, 1952), or are identical with the American 

 one, is not yet known to me. None of these species, however, has reached the 

 Arctic islands of the North Atlantic. 



Ruppia spiralis and Hippuris lanceolata (= H. tetraphylla p.p.) probably 

 belong to this group also, the former so far known only from the Faeroes, 

 Iceland and Greenland in our area. None of the two species is represented on 

 the Arctic islands, but apparently good H. vulgaris has been collected on 

 Bear Island (Ronning, 1959). H. vulgaris, being a freshwater plant does not 

 belong in this group, but H. lanceolata is found in brackish and salt water 

 also along the Arctic coasts of America and Eurasia. No Hippuris of any 

 kind is found at or around the Faeroes, Jan Mayen, Spitsbergen and Franz 

 Joseph's land. 



The number of plant species dispersed over long distances inside our area by 

 sea-currents, thus, are quite few, at most 1.5 per cent of the total flora (cf. 

 Table 3). It has been impossible, furthermore, for this author to find any 

 evidence whatsoever for transport over the open seas of living plant material 

 frozen in ice. It seems highly unlikely that, even if seeds frozen into the ice of 

 a calving glacier could float around in the North Atlantic or the Polar Sea. 

 they would ever reach fhore again (Osborne. 1855: cf also Hulten. 1962). 



