106 =~ Dr. Greville on some new species of Sargassum. 
above the subalpine zone; and there are a few other Pyrenzan 
mosses wanting to the Alps*. 
Two Jungermannia exceedingly common in Britain, Lophocolea — 
bidentata and heterophylla, are all but absent from the Pyrenees ; 
and two others, Jungermannia barbata and Ptilidium ciliare, 
great ornaments of our mountainous districts, are altogether 
wanting. ‘The latter attains its southern limit in the north of 
Italy ; it is distributed throughout middle and northern Europe, 
but grows in greatest luxuriance within the Arctic circle. (Conf. 
Wahlenberg and the accounts of our Northern voyagers.) 
According to Wahlenberg, there are in Lapland, as in the 
Pyrenees, extensive forests of Pinus Abies and P. sylvestris, and 
both descend into the plain ; the former-cease at the altitude of 
800 feet and the latter at 1200 feet, indicating respectively the 
upper limits of the ‘regio sylvatica” and the “ regio subsylva- 
tica.”” But in the Pyrenees these trees ascend proportionally far 
higher than in Lapland ; and that they do not occupy the same 
climatal zones we shall see by comparing the positions of a few 
mosses common to both countries. In the Pyrenees, Tortula tor- 
tuosa, Bryum crudum, Didymodon capillaceus and Dicranum virens 
are found in the region of coniferous trees, and are rarely seen 
above it ; but these are precisely species mentioned by Wahlen- 
berg as characteristic of his “Alpes inferiores,” which are above 
the region even of the birch (“regio subalpina, Wahl.”’), and are 
characterized by the presence of Betula nana, Diapenzia lappo- 
nica and Silene acaulis. Yet the comparative altitudes attained 
by the mosses in the Pyrenees and in Lapland accord very nearly, 
and the species which ascend highest in the one for the most part 
do the same also in the other. Hence the zone occupied by a 
moss common to both has probably in both the same ave 
estival temperature. sbi 
[To be continued. | 
XI.— Alge Orientales :—Descriptions of new Species belonging to 
the genus Sargassum. By R. K. Grevitiz, LL.D. &.t 
[Continued from vol. ii. p. 434.] 
[ With a Plate.} 
WIGHTIANZ. 
10. Sargassum porosum (nob.) ; caule cylindraceo, brevissimo, mu- 
ricato, ramis planis; foliis ovato-oblongis, subundulatis, inciso- 
* The number of species which I have found in the Pyrenees new to the 
flora of France is considerable; but I cannot give a correct list of them, as I 
have not the dates of several species discovered in the Alps and Jura and 
nearly contemporaneously in the Pyrenees, 
+ Read before the Botanical Society of Edinburgh 14th Dec. 1848. 
