VASCULAR PLANTS COMMON TO THE ARCTIC AND THE BRITISH ISLES 93 



region it is counted as native, but in cases of serious doubt - as for instance when collection 

 data have been inadequate - such species have been counted as introduced. 



The symbols following plant names indicate the numbers of vice-counties of Great 

 Britain (112 in all) and Ireland (designated " H " and 40 in all) in which the species 

 concerned is known to occur. Usually these numbers are taken from F.B.I . 

 but in a few cases in which the species concerned or at least the numbers are lacking in 

 that work, they have been supplied from other sources - in particular Druce (1932). 

 In some other instances, recent finds have had to be added to bring the vice-county num- 

 bers more nearly up-to-date. Further symbols have been employed in the case of group 2, 

 comprising plants of sea-shore, lake-margin, aquatic and allied habitats : these indicate 

 the group and sub-group to which each species would have been assigned if it had not 

 been so specially selected. 



There follow the detailed results of this analysis which, although it is in general 

 based on that published in 1939, has the first and third categories somewhat broadened 

 in other ways besides the geographical. There are also unfortunately many of the seemingly 

 inevitable nomenclatural changes. It may be noted that further field experience and 

 general considerations have led to (1) the omission of Luzula arcuata owing to prevailing 

 doubts about its being in full development in the Arctic, (2) changing of Carex lachenalii 

 from a plant of open soil to one characteristically of closed habitats though sometimes 

 found in open areas, (3) changing of the polymorphic and often apomictic Poa pratensis 

 s.l. in precisely the reverse manner, (4) the * sinking ' of Cochlearia groenlandica (which 

 apparently differs from C. scotica and never was a British plant) in the polymorphic 

 C. officinalis s.l., (5) the omission of Senecio congestus (R.Br.) DC. (S. palustris (L.) Hook.) 

 as being apparently extinct in Britain, and (6) the changing of Eriophorum angustifolium 

 from the category of plants of closed communities to that of plants to be found in open 

 areas though characteristic of closed ones. 



1. Plants commonly of open soil or rocky, etc., habitats with little or no competition (although humus may he 

 plentiful) at least in the Arctic. 



(a) found in all three latitudinal arctic zones and of wide distribution meridionally in the Arctic (occurring 

 in at least 5 of the 10 sectors - cf. Polunin 1951, 1954). 



Lycopodium selago - 89, H40. 

 Equisetum variegatum - 34, H21. 

 E. arvense s.l. - 112, H40. 



Cystopteris fragilis s.l. (incl. C. dickieana) - 90, H34. 



V/oodsia alpina - 6. 



Cardamine pratensis s.l. - 112, H40. 



Arahis alpina - 1 . 



Silene acaulis - 25, H5. 



Cer ostium alpinum s.l. - 20. 



Sagina intermedia - 2. 



Minuartia rubella (Wahlenb.) Hiern (Arenaria rubella (Wahlenb.) Smith) - 5. 



M. stricta (Sw.) Hiern (Arenaria uliginosa Schleich. ex DC.) - 1. 



Potentilla crantzii - 21 (incl. recent addition). 



Dryas octopetala - 19, HlO. 



Sedum rosea - 45, Hi 7. 



Saxifraga nivalis - 16, Hi. 



S. hirculus - 10, H6. 



S. cernua - 2. 



S. rivularis - 4. 



S. cespitosa - 3. 



S. aizoides - 33, H6. 



S. oppositifolia - 35, H7. 



Koenigia islandica L. - 1 (not mentioned in F.B.I.) 



