56 
FERNS. 
thirty feet. The tree-ferns have an appear¬ 
ance which effectually distinguishes them^ 
and forms a valuable characteristic in the 
fossil state, namely the regular marks on 
their surface, produced by the periodical 
fall of the leaf. These impressions vary with 
the different leaves of each sort, and as they 
are symmetrically arranged, and of regular 
form, they add greatly to the beauty and 
ornament of the tree. 
Fossil ferns from the coal strata chiefly 
belong to these arborescent kinds, though 
none are identical with existing species. 
Those of our readers who have visited 
the British Museum, will recollect to have 
seen on the principal staircase, the withered 
trunks of two tall tree-ferns from the 
Brazils, with a small crown of leaves, and 
large rough scars on the surface of the stem. 
Individuals of the tribe which thus fur¬ 
nishes us with rarities for the Museum, for¬ 
merly grew where Northumberland and 
Somersetshire now extend over the buried 
treasures of the coal. Such stems, though 
comparitively rare in a fossil state, aie yet 
most decidedly present in that condition, as 
