TRANSACTIONS OF THE SECTIONS. 
75 
is not entirely confined to the branches. In some few stems a similar 
difference has been seen in the opposite sides. In a stem of Pinus.>■ 
Cedrus, for instance, one of the sides was of a pale colour, and had 
the usual structure; the other side was of a darker colour, and had 
a structure similar to that of the under side of horizontal branches. 
Another portion of the same kind of wood, however, was of a uni¬ 
form colour, and had throughout the usual structure. A young 
stem of Pinus laricia had a structure similar to that of branches, 
and the same was observed in an upright stem of Cupressus semper - 
virens. 
On the Formation of Wood. By Dr. West. 
Dr. West exhibited a specimen of Bog Yew, in which, from the 
non-adherence of two successive annual layers, the central portion 
of the heartwood, though in close contact with the surround¬ 
ing portion, which constituted the greatest part of the bulk of the 
tree, was throughout its whole extent perfectly distinct from it, so 
as to present the appearance of a small tree which had grown up 
through the centre of a large one, adapting itself completely to its 
cavity. He considered this singular phenomenon to be the result of 
a severe frost, which had either frozen a very thin layer of albur¬ 
num, so as to destroy its vitality, and thus prevent the next-formed 
layer from adhering to it, or else, without absolutely destroying it, 
had so affected its exterior surface, as to produce the same result. 
He expressed a doubt whether this exactly answered to the lesion 
called by the French gelivure ; and produced a drawing, copied from 
one by Decandolle, of a section of a juniper tree affected with that 
' lesion, in which the diseased layer was of comparatively considerable 
thickness, whereas in his specimen there was no appearance what¬ 
ever of a diseased layer, however thin, nor any space where such 
could have been. He alluded also to another lesion, mentioned by 
Duhamel, called roulure , which consisted in the non-adherence of 
the annual layers, and so far appeared to have a greater resemblance 
to the case under consideration; but for want of a more detailed 
account he did not venture to pronounce whether they were iden¬ 
tical. He next entered into the consideration of how far this case, 
and still more that of Decandolle’s juniper tree, might be urged 
in favour of Duhamel’s theory of the formation of wood, and 
against those of Decandolle and Du Petit Thouars ; and remarked 
that at all events it clearly proved that the bark can form good 
wood, independently of the aid of the alburnum. He further ad¬ 
duced the fact, that the nodules of wood that are found on the trunk, 
of the beech have always a layer of liber interposed between them 
and the alburnum ; and expressed his opinion that this afforded an 
additional proof, that the bark has, in general, if not the sole, at least 
the predominant influence in the formation of wood. In this speci¬ 
men, the annual layer formed after the occurrence, whatever it was, 
that prevented its adhesion to that of the preceding year, was as 
