BOTANICAL NOTES AND NEWS 123 



The Prehistopie Flora of Scotland. — There are many problems 

 with regard to the origin of the flora of every country which cannot 

 be solved by the most careful study of its existing condition. It 

 is frequently not possible to ascertain with confidence from what 

 source, and when, and in what manner certain species immigrated ; 

 and this is peculiarly the case where man has long been a dweller, 

 and has efl'ected great changes, as has been the case even in Scotland. 

 Any light from early sources is most welcome ; and among the 

 more important sources of light are the investigations of the 

 tertiary and more recent deposits. Mr. F. J. Lewis has been doing 

 admirable work in his study of the peat mosses in several districts of 

 Scotland from the south to the Shetland Islands and the Hebrides, 

 the results of which are published in memoirs noted in this issue 

 under " Botanical Literature." Mr. Lewis has been able to show 

 the very wide occurrence of two forest-beds in the South of Scotland, 

 of which the lower gave place to an arctic flora, followed by the 

 upper forest deposits, which in their turn were succeeded by the 

 existing covering of moors and swamps. In the north he has not 

 found the lower forest-bed ; the other strata are present in the same 

 order, except that the single upper forest-bed of the south is repre- 

 sented by two, between which is Sphagnum peat, from one to three 

 feet thick, from which wood is quite absent. The upper of the two 

 layers usually shows Pinus sylvestris, the lower Betiila alba ; and the 

 intermediate peat yields Salix Arbuscula^ Betula nana^ and other 

 plants characteristic of a climate unsuited to the growth of trees. 

 No corresponding true forest-bed was found by Mr. Lewis in the 

 Hebrides and in Shetland, although Betula alba^ Alnus, and Corylus 

 occurred in a layer probably corresponding to the lowest forest-bed 

 of Southern Scotland. 



From the investigations of the past three years Mr. Lewis finds 

 that the following stages are represented in Scottish peat mosses : — 



I. Recent peat. 2. Upper forestian, including in Northern 

 Scotland an upper and a lower forest-bed separated by from one to 

 three feet of Sphagnum peat with subarctic plants, the upper forest- 

 bed being the earliest to show extensive Vaccinium-Calluna deposits. 



3. Upper peat bog, of existing species of peat bogs and marshes. 



4. Second arctic bed, with remains of arctic plants, now existing on 

 our hills in a few localities only, along with others that indicate that 

 the climate was not so extremely cold as might have been supposed 

 from the presence of the arctic alpine plants. 5. Lower peat bog 

 containing remains of plants like those of present time, except in 

 absence of Calhaia. 6. Lower forestian containing remains oi Betula 

 alba, Alnus, and Corylus, along with numerous herbs indicating a 

 mild climate. 7. First arctic bed containing remains of Betula 

 nana, Salix, Arbuscula, and other plants of a cold climate. In a 

 summary, with comparative diagrams of the limits about the sea-level. 



