88 Mr. R. Spruce on the Musci and Hepatice 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 Pyrénées and part of the Landes, stretching 
as far as the Adour at St. Sever and Dax, besides a small portion 
of the Hautes Pyrénées; in Spain, a small part of Navarre 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 Arriége and Pyrénées 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 
Néouvielle (9696 ft.), as some maintain. In the eastern part of 
the Western Pyrenees it constitutes the mass of the mountams 
above Cauterets, especially those which include the valleys of 
Combascou, Lutour and Jéret, and the Lac de Gaube; from 
whence it passes (by the Vallée d’Azun, &c.) into the upper part 
of the Vallée d’Ossau, where I have observed it from below the 
Eaux Chaudes to the Pic du Midi, and on the cireumjacent moun- 
tains, in which it is the predominant rock. From the Vallée 
@’Ossau it dips at once sv profoundly as not to be observed in 
the deepest parts of the Vallée d’Aspe, or im 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 
Baréges (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 Arriége 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 Pies 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. 
