88 Mr. R. Spruce on the Musci and Hepatica of the Pyrenees. 



branches of the Adour and Garonne, and contains the highest 

 mountains and the deepest valleys in the Pyrenees, as well as the 

 most extensive forests. Glaciers of great extent are found in this 

 district only ; the principal are those which occupy the northern 

 slopes of the Maladetta and Crabioules. 



The Western Pyrenees extend from the Central to the ocean 

 at Bayonne and St. Jean de Luz. They include, in France, the 

 Dept. of the Basses Pyrenees and part of the Landes, stretching 

 as far as the Adour at St. Sever and Dax, besides a small portion 

 of the Hautes Pyrenees ; in Spain, a small part of NavaiTC and 

 most of the northern part of Aragon. This district extends 

 farther to the north than either of the others ; it is consequently 

 colder at the same altitude, and in the sandy plains bordering 

 on the Adour and the ocean the climate is much more humid. 



The Eastern Pyrenees are comprised between the Central and 

 the Mediterranean. In France they occupy the whole length of 

 the Depts. of Arriege and Pyrenees Orientales ; in Spain, nearly 

 all the northern part of Catalonia. This district is the most 

 southern, the warmest and driest, and the most denuded of 

 forests of the whole three*. 



A rough sketch of the mineralogy of the Pyrenees, so far as it 

 is connected with the distribution of plants, will conduce to a 

 more complete idea of the peculiarities of these divisions. The 

 igneous rocks of the Pyrenees do not, as in the Alps, constitute 

 some of the loftiest mountains, and the highest point at which 

 I am aware of the existence of granite is on the summit of the 

 Pic du Midi d'Ossau (9186 ft.), unless it attains the summit of 

 Neouvielle (9696 ft.), as some maintain. In the eastern part of 

 the Western Pyrenees it constitutes the mass of the mountains 

 above Cauterets, especially those which include the valleys of 

 Combascou, Lutour and Jeret, and the Lac de Gaube; from 

 whence it passes (by the Vallee d^Azun, &c.) into the upper part 

 of the Vallee d^Ossau, where I have observed it from below the 

 Eaux Chaudes to the Pic du Midi, and on the circumjacent moun- 

 tains, in which it is the predominant rock. From the Vallee 

 d^Ossau it dips at once so profoundly as not to be observed in 

 the deepest parts of the Vallee d^Aspe, or in any of the valleys 

 to the westward, until it reappears near Bayonne, in the massif 

 of Cambo. In the Central Pyrenees it appears in the valley of 

 Bareges (continued from the valley of Cauterets) and about the 

 base of the Pic du Midi de Bigorre ; but, with this latter excep- 



* I should add, that great part of the Arriege is still a terra incognita to 

 me, and I especially commend its exploration to resident cryptogamists. 

 Probably, from its containing some very lofty summits, as the Pics of Mont- 

 calm and Estats, both its character and its vegetable products would require 

 the western part of it to be annexed to our Central district. 



