The Flora of Greenland and its Origin. 35 



and Hieracia from the most southern paris will probably 

 add to the number of endemic species in tliese two genera. 



As a rule, endemic species olTer little of inlerest in 

 phyto-geographical respects; with some of those here men- 

 tioned, however, it is otherwise. Of little value in this respect 

 is Braya Thorild-Wulffii, a high-arctic species, closely allied 

 to the widely distribnted B. purpur ascens; it will probably 

 also be found in the adjoining parts of arctic America. 

 Potamogeton groenlondicus is a little known species, which 

 has only been found as sterile, and has been described from 

 anatomicai features (Hagstrom 1916); it is related to P. 

 mucronatus (P. Friesii). and may also perhaps occur in 

 arctic America. 



The other endemic species belong to 3 genera, all of 

 which are peculiar by the faet that their sex conditions are 

 abnormal; a large number of the species, including all the 

 arctic ones (as far as known), are apogamous (i. e. form seeds 

 without fertilisation), so that any new micro-species arising is 

 atonce fixed, and cannot be effaced by crossingback with the 

 parent species. Of these endemic species, there is no special 

 reason to dwell on T. arctogenum and Antenuaria inter media; 

 the 4 Hieracium species on the other hånd, are of particular 

 interest as belonging to sections within the genus not found 

 in arctic America at all.^ And since they are also mainly 

 found within the region formerly occupied by the Norsemen, 

 it seems most likely that they are descendants of Hieracia 



' Since this was written Professor M. L. Fehnald lias kindl}' informed 

 me that in 1925 he found a Hieracium on north-western New Foundland 

 whicli he cannot distinguish from //. groenlandicum. This interesting 

 record may have a far-reaching intluence on tlie theory put forward here, 

 but I prefer at present to suppose that the New Foundland jjlant has 

 arrived thither from Greenland, the achenes of Hieracium being well 

 adapted to be carried by wind. 



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