LI.XNBAN SOCIETY OF LONDON, 87 



stippled shading. The significance of the high percentage of 

 httorals on the East coast of Great Britain becomes still more 

 manifest if we consider that this region is at the same time the 

 poorest in Southerns, numbering 75 out of the total of 134 (56 

 per cent.) against 102 (76 per cent.) for the West and 122 (91 

 per cent.) for the South. That is, the eastern zone is not only 

 least endowed with Southerns, but owes much of its share in that 

 element to the presence of littorals, many among them moreover 

 species of wide distribution. However much the shatling in map 1 

 \\ould generally be toned down by the exclusion of littorals, the 

 relative unevenness of the distribution of the Southerns in Great 

 Britain as compared with Ireland would not only be maintained 

 but distinctly enlianced. That is only wliat might be expected 

 from the geogi'aphical positions and tlie sizes of the two islands. 



There is one more aspect in the diffusion of the Southerns in 

 the British Isles which is not directly deducible from the map, 

 namely the relative share of the floras of each island in Southerns 

 computed on the number of species of each flora. Of the 142 

 Southerns 134 are found in Great Britain and 81 in Ireland, which, 

 expressed in percentages of the two floras, works out at about 

 9 per cent, of each of them, or, if we distinguish between the 

 English and Scottish floras, at 9 per cent. (English) and 5-3 per 

 cent. (Scottish). 



Atlantic Elements (Map 2), — The character of the Atlantic 

 elements as a well-defined type of distribution is so clearly demon- 

 strated in the inset map that it calls for no special comment. The 

 main map shows the Atlantic element strongly represented in the 

 South of England, but the zone of maxima also extends without 

 interruption northwards along the west coast as far as Anglesea, 

 thus connecting the small detached Welsh maxima zone of map 1 

 with the southern belt. The Atlantic element is still numerous 

 farther north on the same coast as far as the Clyde and the Island 

 of Mull. Further, a zone rich in it skirts the whole of the southex'n 

 half of Ireland, whilst two smaller detached areas marked 

 black in the map point to a junction with the south-west of Scot- 

 land and Westiiioreland. Inland, and in England north and 

 eastwards, the Atlantic plants become less numerous, but they 

 nowhere sink to the level marked by blanks. 



Numerically the total of the Atlantic species amounts to 45"8 

 per cent, of the Southern element, but they are so distributed over 

 Great Britain and Ireland that they are relatively less numerous 

 in the larger island (44"75 per cent.) than in the smaller (55*25 

 per cent.). Thus they predominate among the Southerns of 

 Ireland. These figures include the littorals, which are repre- 

 sented in Great Britain as well as in Ireland in the proportion of 

 two Atlantics to three Mediterraneans. If we eliminate them the 

 preponderance of the Atlantic strain in Ireland becomes still more 

 marked. It rises to 61 per cent., the corresponding figure for 

 Great Britain being 47*7 per cent. 



