LINNEAN SOCIETY OF LONDON. 9 1 



Of the minority with pronounced discontinuity of area the follow- 

 ing have to be mentioned : the distribution of some of them is 

 illustrated by maps (6-11), which have been so selected as to 

 show increasing degrees of discontinuity. Erica ciliaris (map 6) 

 inhabits only 3 small mucli separated areas in the British Isles, 

 but their connection with its wide continuous continental area is 

 quite clear. Simethis hicolor (map 7) with 2 small detached areas 

 in the British Isles is linked to its extensive continental area by 

 an outpost on the lower Seine. Arhtitus Unedo (map 8) with its 

 solitary Irish area is similarly joined to its continental area — 

 though the gaps are wider— by its station in tlie Cote du Nord. 

 Euplwrhia hiherna has its northern limit in the department of the 

 Sarthe, Daboecia Poli folia (map 9)iu that of the Maiue et Loire, 

 both in the latitude of Brittany, but to the east and south of the 

 peninsula; Ecliium plantagineum m the Vendee; Matliiola incana 

 and Atropis Foucaudii in the Charente Inferieure ; Erica 

 mediterranea in the department of the Grironde. A further 

 srep of less than 2 degrees brings us to the latitude of the Pyrenees 

 and the Asturian mountains, which harbour a number of plants 

 whose British stations are the only ones north of that latitude. 

 They are ^I rrt 6 is stricta, Hypericum, undulatum, Saxifraga 

 Geum and S. umbrosa, Physospermum cornubiense, Piiigui- 

 cula grandiflora, Erica Mackaii (map 10), Neotinea intacta 

 (map 11) and Trichomanes radicans. It is this small group 

 which with some justification might be designated as " Pyre- 

 nean " or " Cantabrian," although Physospermum cornubiense and 

 Neotinea intacta have a wide range in the Mediterranean countries. 

 Arabis stricta inhabits a very much broken-up area in Southern 

 Prance (from the Pyrenees to Sa\oy) and in Spain. Hypericum 

 undulatum is considered by some botanists as approaching so 

 closely to the widely distributed H. quadrangidum that it is 

 treated by them as a western variety of it. Trichomanes 

 radicans occurs in the warm regions of both hemispheres, and 

 is evidently a relict of very great age. Like the remaining species 

 of the group it fits very naturally into the assemblage of Atlantic 

 plants in the British Isles. Apart from the so-called North 

 American species, the remaining four species Saxifraga Geum 

 and >S'. umbrosa, Pinguicula grandiflora and Erica Mac- 

 haii are often quoted as the most puzzling instances of distri- 

 bution among the British plants, and they have attracted the more 

 attention, as they are, within the British Isles, confined to the 

 extrenie south-west and west of Ireland. The anomalies of their 

 distribution are, however, more apparent than real, and, considered 

 side by side with the distribution of the other members of the 

 Southern stock, they resolve themselves into cases of far-gone 

 disintegration of area. How this has come about, or how the 

 Atlantic and Mediterranean elements of the British flora have 

 arrived in their island home, is a question which cannot be dealt 

 with in this place. 



