522 



0. Stapf. 



total of the southern elements or the proportion of the Atlantic and 

 Mediterranean shares. 



The British areas of the littoral southern element generally join on 

 to the continental areas so that there is no marked discontinuity^ the only 

 exceptions being Mathiola incana (Isle of Wight to Charente inferieure), 

 Limonium hellidifolium (Norfolk to the eastern end of the French- 

 Spanish frontier), Atropis fcstuciformis (Co. Down in Ireland to S. Se- 

 bastian in North Spain), and eventually Atropis Foiicaudii (estuaries 

 of the Shannon and the Thames to the mouth of the Charente). All these 

 with the exception of the first are salt marsh plants which are particu- 

 larly liable to casual introduction and may easily get a foothold on weakly 

 tenanted ground. 



Non-littoral species. The 95 species enumerated in the second table 

 are distributed in the British Isles as follows: 



Great Britain: 87 (Atl. 41 or 47 p. c, Med. 46 or 53 p. c.) 

 Ireland: 57 (Atl. 35 or 61 p. c, Med. 22 or 39 p. c). 



There is thus among the southern element a slight preponderance of 

 Mediterranean plants in Great Britain and a decided predominance of At- 

 lantic plants in Ireland. 



Generally distributed through both islands, or the greater part of both, 

 are Hypericum Androsaemum.^ Ilex Aqui folium j TJlex europaeus^ Apiiim 

 nodifhrum^ Conopodiiim majus ^ Oenanthe crocata^ Cardutis pycno- 

 cephahis^ Ei^iea Tetralix^ E. cinerea^ Scilla non-scripta and general 

 in Great Britain, but much restricted in Ireland, Corydalis claviculata. 

 This means that the Atlantic element is very prominent among the most 

 widely diffused of the southern species, and its predominance appears still 

 more marked if we take into consideration that the general presence of 



nodi/l 



whalus 



bably due to their great facilities for extending their area, the former as 

 an aquatic, the latter as a waste land plant. The absence in Ireland of a 

 plant very widely spread in Great Britain, Genista anglica^ an Atlantic 

 species, is very remarkable, and to it might be added Tamus communis^ 

 so common in England and yet doubtful as a native in Ireland. On the 

 other hand widely distributed in England and Ireland are Lepidium 



Tmi- 



Hypericum elodes, TJlex Gallii, Cotyledon Im 

 hilicus and SecJum angllcum, all but one Atlantic members of the 

 southern element. Another group of species of fairly wide distribution is 

 worth noting on account of the fact that they are absent from the greater 

 part of the eastern counties of England, but extend through North England 

 and Scotland to the north east coast. They are Vicia Orobus, Saxi- 

 fraga hypnoides, Scilla verna, Hymenophyllum tunhridgense, 

 H. peliatum and Lastraea aemula, all Atlantic species which are 

 also found in Ireland. The Atlantic element is also prevalent among the 



