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



that is, by certain plants which constitute a marked feature in 

 them, it would seem at first sight a great advantage could we se- 

 lect in every country the same species for this purpose ; but a little 

 research will suffice to show us the impracticability of this. To 

 go no farther than the Alps ; near as they are to the Pyrenees, and 

 similar as their vegetation is in many respects, there are yet im- 

 portant differences. While, for instance, there is no tree in the 

 Alps above the region of the spruce-fir (Pinus Abies, L.), in the 

 Pyrenees there is above this a broad and well-marked belt of 

 Scotch fir [Pinus sylvestris, L.). Again, there is in the Alps, 

 above the limit to which the oak ascends, a zone in which the 

 birch [Betula alba, L.) is the predominant tree; but in the 

 Pyi-enees the birch is excessively rare ; indeed I do not at this 

 moment recollect having anywhere seen it where I could be cer- 

 tain it had not been planted, and I perceive Mr. Bentham in- 

 cludes it in his catalogue with a mark of doubt. It would also 

 be quite impossible to define any of our climatal zones in the 

 Pyrenees by the distribution of the heaths, as has been done for 

 the British Isles by Mr. Watson in his ' Cybele Britannica.' The 

 only " heath-clad hills " I have seen in the Pyrenees, reminding 

 me of our English and Scottish hills, are some of the lower 

 mountains around Bagneres-de-Bigorre, and here the prevailing 

 species is Erica vagans, though Calluna vulgaris occurs also, 

 sparingly. The latter species seems never to penetrate far into 

 the mountains. Again, Erica tetralix is not found at all in the 

 Central or Eastern Pyrenees, but only in the Western. The 

 only heath I have remarked near Bagneres-de-Luchon is Erica 

 cinerea. E. arborea is abundant in the valley of Argelez and its 

 tributary valleys (Castelloubon, &c.), but is absent from the Cen- 

 tral Pyrenees, while it reappears in several parts of the Eastern. 

 It has been shown by M. des Moulins ("Etat de la Vegetation 

 sur le Pic du Midi de Bigorre, &c. /^ ' Recueil des Actes de 

 P Academic Roy ale de Bordeaux,^ 1844), that several species of 

 thistles occupy zones of altitude in the Pyrenees which are easily 

 ascertained, and he has actually constructed a scale of the dis- 

 tribution of fourteen species in the Pyrenees Centrales, showing 

 the altitudes at which they appear and disappear. But were 

 this scale taken as the basis of a climatal arrangement (which M. 

 des Moulins by no means proposes), how would it assist us in 

 comparing the flora of the Pyrenees with that of Lapland, where 

 according to Wahlenberg, " Cardui in sylvis admodum rari, 

 omnesque fere inermes sunt. De ca^tero quoque plantse vel 

 frutices aculeati in Lapponia non crescunt, &c. '^ ? 



In comparing two distant portions of the earth's surface with 

 each other, in both of which the same plant is extensively distri- 

 buted, we are not hence to conclude that the zone which it oc- 



