476 REPORT—1883., 
besides this, we are much richer in huge Lepidodendroid and Sigillarian trees, 
with their Stigmarian roots, than the French are; hence we have a vast mass of 
material, illustrating the history of these types of vegetation, in which they seem 
to be seriously deficient. This fact alone appears to me sufficient to account for 
many of the wide differences of opinion that exist between us respecting these trees. 
My second difficulty springs out of the imperfect state of our knowledge of the 
subject. One prominent cause of this imperfection lies in the state in which our 
specimens are found. They are not only too frequently fragmentary, but most of 
those fragments only present the external forms of the objects. Now, mere 
external forms of fossil plants are somewhat like similarities of sound in the com- 
parative study of languages, They are too often unsafe guides. On the other 
hand, microscopic internal organisations in the former subjects are like grammatical 
identities in the latter one. They indicate deep affinities that promise to guide 
the student safely to philosophical conclusions. But the common state in which 
our fossil plants are preserved presents a source of error that is positive as well 
as negative. Most of those from our coal-measures consist of inorganic shale, 
sandstone or ironstone, invested by a very thin layer of structureless coal. The 
surface of the inorganic substance is moulded into some special form dependent 
upon structural peculiarities of the living plants, which structures were sometimes 
external, sometimes internal, and sometimes intermediate ones. Upon this inor- 
ganic cast we find the thin film of structureless coal, which, though of organic 
origin, is practically as inorganic as the clay or sandstone which it invests; but 
its surface displays specific sculpturings which are apt to be regarded as always 
representing the outermost surface of the plant when living, whereas this is not 
always the case. That the coally film is a relic of the carbonaceous substance of 
the living plant is unquestionable ; but the thinnest of these films are often the sole 
remaining representatives of structures that must originally have been many inches, 
and in some instances even many feet, in thickness. In such cases most of the 
organic material has been dissipated, and what little remains has often been 
so reconsolidated as to be merely moulded upon the sculptured inorganic substance 
which it covers, hence it affords no information respecting the exterior of the fossil 
when ‘a living organism. It is, in my opinion, specimens like these that have 
caused the smooth bark of the Calamite to be credited with a fluted surface, and 
the Trigonocarpons with a simply triangular exterior and a misleading name, as it 
long caused the inorganic casts known as Sternbergiz to be deemed a strange form 
of plant that had no representative amongst living types. In other cases the outer- 
most surface of the bark is brought into close contact with the corresponding surface 
of the internal vascular cylinder. I have a Stigmaria in which the bases of the root- 
lets appear to be planted directly upon that cylinder, the whole of the thick inter- 
mediate bark having disappeared. In other examples that vascular zone has also 
gone. Thus the innermost and outermost surfaces of a cylinder, originally many 
inches apart, are, through the disappearance of the intermediate structures, brought 
into close approximation. In such cases, leaves and other external appendages 
appear to spring directly from what is merely an inorganic cast of the interior of 
the pith. I believe that many of our Calamites are in this condition. Such 
examples have suggested the erroneous idea that their characteristic longitudinal 
flutings belong to the exterior of the bark. 
Fungi.—Entering upon a more detailed review of our knowledge of the 
Carboniferous plants, and commencing at the bottom of the scale, we come to 
the lowly group of the Fungi, which are unquestionably represented by the Perono- 
sporites antiquarius! of Worthington Smith. There seems little reason for 
doubting that this is one of the Phycomycetous Fungi, possibly somewhat allied to 
the Saprolegniee ; but since we have, as yet, no evidence respecting its fructification, 
these exact relationships must, for the present, remain undetermined. So far as I 
know, this is the only Fungus satisfactorily proved to exist in the Carboniferous 
rocks, unless the Excipulites Neesti of Goeppert and one or two allied forms belong 
to the Fungoid group. The Polyporites Bowmanni is unquestionably a scale of a 
Holoptychian fish. 
1 Memoir xi. p. 299. 
