498 British Association for the Advancement of Science. 



But although the upper and under sides of many, perhaps all, co- 

 niferous branches, present a different structure, yet such a difference 

 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 

 Cedrtts, 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 

 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. 



