50 Dr Martius on Antediluvian Plants. 
times densely, at other times sparsely diffused over it, and arti- 
culated by an elliptical or rhombiform base, and fall off at the 
end of two or three years, leaving cicatrices of various forms 
upon the surface of the stem 
In their mode of growth, therefore, the tree-feras are very 
similar to palms, the evergreen stem of which throws off the 
fronds which are inserted into the bark, in the space of about 
three years, and is then marked with transverse rings, from the 
insertion of the base of the petiols ; they differ, however, from 
palms, in this respect, that, as the base of the petiols is not am- 
plexicaul, the fronds,, on falling, do not leave annular cicatrices, 
but of various forms, according to the base of the stipes. The 
more robust the stipe of the frond, the deeper it is inserted into 
the stem, and the more marked the cicatrix which it leaves. We 
see some species, such, for example, as Polypodium corcova- 
de7ise, whose rhombiform and deeply impressed cicatrices are 
so approximated as to occupy almost the whole surface of the 
bark ; others again, and those of very frequent occurrence, have 
a portion of the bark between the petiolar cicatrices free, and 
exhibiting areas of various forms. This part of the surface is 
covered with palece^ which in some are more densely, in others 
more sparsely arranged, erect, arid, commonly lanceolate, or 
oblong, entire at the margin, or variously fringed, investing the 
stems, especially when young, with a singular rough covering, 
and at length gradually falling off, or becoming obliterated. 
These paleaceous appendages derive their origin from the epi- 
dermis of the caudex, which is either smooth, or elevated into 
warts, tubercles or wrinkles ; and as they are, for the most part, 
arranged in a very dense body, in young plants, or those which 
have suffered little from external injury, they usually conceal 
entirely the singular, and, in so far as I know, hitherto unde- 
scribed structure peculiar to all the stems of ferns. This pecu- 
liarity consists in the bark’s being excavated by scrobiculi, either 
elliptical or oblong, from one to two lines in depth, and from 
* These cicatrices have been called Laubansatze by the celebrated Nees Von E- 
senheck, in his excellent Handbuch der Botanik, 1. p. 243., but they have nothing 
in common with stipules, nor are they properly organs at all, but merely the 
marks left by the stipules after they have fallen off. 
