18 PROCEEDINGS OF THE 



Arbutus Unedo, Erica ciliaris, TricJwmanes radicans, Gymnngramma 

 leptophjlla, etc. These are found with us only in the soutli and 

 south-west of England and Ireland, and as they are all natives of 

 the warmer parts of continental Europe, they may be regarded as 

 having reached their utmost northern limit in the southern parts 

 of Britain. On the other hand, Linncea borealis, and the beautiful 

 little Primula Scotica, both denizens of a colder climate, appear to 

 have reached their southern limit in the northern half of Scotland. 

 There are others, such as the orchids of the chalk counties, the 

 distribution of which appears to be regulated wholly by the nature 

 of the soil. Diijitalis purpurea furnishes us with a more common 

 illustration of the influence of soil in determining the habitat of a 

 species. It abounds on all the trap-hills of Scotland, but entirely 

 disappears wherever the substratum is composed of limestone. 

 Proximity to the sea appears to be a powerful element in regulating 

 the distribution of a large number of plants. Glaux maritima, 

 Salsola Kali, Brassica monensis, Cahjstcgia Soldanella, Eryngium 

 maritimum, and many more, may be looked for in vain anyTvhere 

 else than in the immediate neii^hbourhood of the sea. Armeria 

 maritima, Cochlearia officinalis, etc., likewise grow abundantly on 

 our shores, but they entirely disappear a few yards beyond high 

 water mark, and, strange to say, make their appearance again on 

 the tops of our liighest mountains — ^as Benlawers, for instance, a 

 locality as far removed from the sea as any within the bounds of 

 Scotland. Is it not possible they may be more under the saline 

 influence of the ocean, on the mountain tops, than they would be 

 anywhere else, except on the shore? The mountains, too, have 

 their OAvn peculiar flora. Saxifraga cernua, nivalis, stellaris, 

 opposiiifolia, Veronica saxatilis, Alchemilla alpina, etc., etc., never 

 descend from their elevated position of their accord ; yet they all 

 bear transplanting well, and will flourish in any garden without 

 the least care being bestowed on them. The distribution of all 

 tliese — and many more might be added — is pretty satisfactorily 

 accounted for, either by soil, climate, exposure, or elevation, 

 with the exception of the few anomalous sea-side species that 

 are likewise to be met with on the mountain tops. There are 

 others, however, the distribution of which can be satisf;xctorily 

 explained neither on the principle of latitude, temperature, 

 chmate, or soil, but which appear to depend on some other law 

 or laws not easily to be perceived or understood. Scandix Pecten- 



