90 Mr. R. Spruce on the Musci and Hepatica of the Pyrenees* 



ley of Cauterets it would seem to be entirely absent^ but it re- 

 appears in the Central Pyrenees in the great valley of Bareges, 

 where it extends from the bottom of the valley of Gedre to a little 

 beyond the lake of Gavarnie, and plunges under the immense 

 mass of alpine limestone of the Marbore. The lower hills near 

 B.-de-Bigorre, especially the Pic de Lhieris, are formed almost 

 entirely of it_, and here it often presents itself in thin beds, alter- 

 nating with clay-slate. In the upper part of the valley of Lu- 

 chon, and in all the surrounding mountains, I do not recollect 

 to have observed any calcareous rock. In the E. Pyrenees, 

 transition-limestone would seem to occur amongst the granitic 

 formations in detached masses (accompanied however by slate) 

 chiefly in the neighbourhood of Villefranche and Prats de Mollo, 

 and in the Corbieres. The ascents of mountains of transition- 

 limestone are interrupted by escarpments, which are rarely of 

 great elevation. 



Of secondary rocks, the only one which I shall have occasion 

 to mention is oolitic limestone (calcaire alpin). To this rock the 

 Pyrenees owe some of their grandest features, as it forms escarp- 

 ments in some instances considerably exceeding a thousand feet 

 in altitude, as at the Cirque de Gavarnie, the termination of the 

 Vallee d^Estaube, &c. ; but wherever it attains the alpine region 

 (as in the instances just cited) I have found it quite destitute of 

 mosses, probably from its exposed position, above the region of 

 forests. It is only in the lower hills of the Western Pyrenees, 

 especially near Pau, where it occurs as a conglomerate, that the 

 alpine limestone has afforded me any cryptogamia. Some of 

 Dr. Arnott's mosses from the Pyr. Orientales, judging from the 

 fragments attached to the specimens, have been gathered on 

 alpine limestone. 



Trap-rocks I have remarked in the Pyrenees in small detached 

 masses, but I have gathered cryptogamia only on a rapidly de- 

 composing ophite at Labassere near B.-de-Bigorre, and at St. 

 Pandelon near Dax. 



This brief sketch of the chief rocks of the Pyrenees is confessedly 

 very imperfect ; it is also designedly superficial, for it is only by 

 the surface-rock that plants whose roots rarely penetrate to the 

 depth of an inch can possibly be influenced. The position, too, 

 of any rock in the geological series cannot be said to have any- 

 thing to do with the distribution of plants, though the presence 

 of a certain mineral is in many cases essential to their existence. 

 From my observations in the Pyrenees and elsewhere, I have 

 ascertained pretty accurately what mosses require a matrix con- 

 taining carbonate of lime ; these will be specified as they occur. 

 They have obviously no preference for primitive, transition, or 

 secondary limestone, but they are always most abundant and 



