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rot nn exceptional vegetation in this chain of mountains, and if it be ex- clusively Scandinavian, that of the whole Jurassic flora is equally so. But in answer to this objection, read the list in Tliurmann's ' Essai Ph\to- staticfue of the characteristic mountainous plants of the chain ; of these, there are 142 species mentioned, out of which only 66 exist also in Scandinavia. The presence of these Arctic species in the Jurassic turf- bogs, is then a confirmation of the opinion that they existed in the Jura at the "ilacial era. All, in fact, can support a temperature lower than that of the Jurassic peaks, for all ascend higher in the Alps, and they can ac- commodate themselves to a more temperate climate, for I have gathered tliem nearly all in the north of Norway at the sea-level. Another conse- quence of these facts is, that the vegetation of all the peat-mosses of the plains of northern Europe, of the Vusges, the hills of Anvergne, the Alps from France to Austria, and even of the Pyrenees has the same origin. Por long botanists have been' struck with the uniformity of their vegeta- tion, and attributed it to a similarity of physical conditions. This ex- plains why the plants stfiy there, but it does not explain why we always get the same species over a space equal to a quarter of the area of the whole terrestrial globe. Identity of origin can alone explain this identity of vetictable forms.
��lefa) Bublicatmns.
��The Llchen-Flura of Great Britain, Irela)id, and the Channel Islands. By the Rev. W. A. Leighton, F.L.S. 12ino. Shrewsbury, 1871.
Within the last ten years no less than three Synopses, or systematic enumerations, of the British Lichens have been published in this country, viz. Mudd's 'Manual of British Lichens,' in 1861; the Rev. J. M. Crombie's ' Lichenes Britannici,' in 1870; and the work whose title heads the present remarks, in 1871. The significance of this circumstance must be interpreted by the correlative fact that, between 1844, when the second edition of the well-known ' English Botany' of Smith and Sowerby was issued, and 1861, no work of a similar kind had appeared ; for Leigh- ton's ' British Species of Angiocarpous Lichens ' (1851), and other mono- graphs of his, referred only to certain groups ; while Lindsay's ' Popular History' (1856) did not profess to be a conqjlete or systematic Lichen- flora, being intended simply as an Introduction to the study of the liritish Lichens. The three works first above mentioned, especially as compared with those which appeared prior to 1850, mark an era in British lichenology, in so far as they are all the fruits of the application of the hiicrosco/je to the detinition and classification of genera and species. This instrument was virtually unknown to, or unapplied by, the authors of the various Lichen-floras of Britain — of England, Scotland, or Ireland — before the year 1850 ; the only artificial aid to the naked eye in the examination of external or internal characters being, up to that date, the common pocket lens. The result of the introduction of the microscope iu the examination and determination of Lichen-species lias not been altoge- ther an advantage. It lias destroyed the comparative sinq)licity of classi- fication and nomenclature, and has snbstitutcsd, for the intelligible arrange- ments of Aeharius, Fries, and Schiurer, tlie confusingly elaborate "systems" of Massalongo, Korbcr, and Nylander. Too much is now made of micro-
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