Mr. R. Spruce on the Musci and Hepaticce of the Pyrenees. 97 



cupies has in both countries the same average annual temperature. 

 Were this the case, such discrepancies as the following would be 

 inexplicable. On Mount Etna, the beech, the birch and the 

 Scotch fir are said to occupy the same zone. In the Pyrenees 

 the beech ceases before the Scotch fir begins, and in the Alps 

 the birch is said to fail even below the spruce-fir. But in Lap- 

 land the birch extends far above the Scotch fir, and in fact 

 ascends higher on the mountains than any other tree. Assuming 

 the correctness of these observations (which for Lapland and the 

 Alps cannot be questioned), we are bound to conclude that there 

 are peculiarities of constitution in certain species which enable 

 them to ascend proportionally higher in one latitude than in 

 another *. Li other words, an alpine flora is not necessarily an 

 arctic flora, in its character. Hence the saying of Linnaeus, 

 "Plantse diversse indicant altitudinem perpendicularem terrse," 

 must be regarded not as an axiom but as a problem, the complete 

 solution of which still remains to be effected. 



It will readily be admitted that all our artificial arrangements, 



* The discussion of this idiosyncrasy would demand an entii'e volume, 

 but Wahlenberg's explanation of it (Flora Lapponica, Introd.) is worth 

 quoting, and should be borne in mind in comparing the flora of the Pyrenees 

 or of the Alps with that of Lapland. " Valde probabile mihi videtur a calore 

 vieridiano vegetationisgradum praecipue pendere "(p. xlix, 1. c.) — '■^Temperies 

 tantum ilia astivalis in vegetatione producenda efficax, constituit clima, 

 ejusque gradus determinat." (p. Hi.) — " Aliae plantas longam magis, quam ca- 

 Udam cestatern sibi exposcunt: ubi temperatura jBstivalis media perti-es men- 

 ses gradum 8°"5 (Centigr.) baud attingit, ibi hordeum baud ad maturitatem 

 pervenire potest. Hoc quidem jamdudum infra Enontekis contingit ; sed 

 nihilominus tamen arbores varife aestate brevi et calida hujus regionis con- 

 tentae sunt : Betulse enim et Salices alpes versus longe altius l^te propa- 

 gantur. Arbores coniferse fere ac Hordeum aestatem longiorem quamquanr 

 temperatiorem, requirunt, itaque longe altius ascendunt in alpibus Helve- 

 ticis quam Betula, &c. Ex observationibus thermometricis ailatis constat, 

 eestatem in alpibus Helveticis, etiamsi temperatior sit, fere longiorem esse, 

 quam in alpibus Lapponicis ; et pro certo scimus, temperaturam mediam 

 omnium mensium per totum annum eo magis aequabilem esse in montibus 

 Andium Americae meridionalis, et igitur omnes arbores, calidiorem quam 

 longiorem aestatem requirentes, ibi crescere desinunt dupio longius infra 

 limitem nivalem quam apud nos ; sed Hordeum aliaque Cerealia temperie 

 moderata 7 vel 8 graduum contenta, si ea modo longior sit, duplo altius 

 versus limitem nivalem ibi adscendunt quam omnes arbores." (p. liii.) 



It is also well known that some plants will hea.r forcing, that is, will sur- 

 vive and flourish under constant excitement and irritation, much better than 

 others ; hence we could hardly expect any plant which will not bear some 

 degree of forcing, to thrive in the rapid summer, with its long days and 

 proportionally great meridional heat, of countries bordering on the Arctic 

 circle; should it even subsist through the I'igorous winter of that region. 



I am sensible how much the absence of exact thermometrical observa- 

 tions takes away from the completeness of this sketch of part of the flora 

 of the Pyrenees. I have none of my own to adduce, except a few made at 

 the foot of the Western Pyrenees in the month of June, when I found the 

 meridional temperature to often exceed 90° Fahrenheit. 



Ann. ^ Maff. N. Hist. Ser. 2. Vol. iii. 7 



