Botanical Society of Edinburgh. 343 



anatomy of the Coniferee coincided with their general structure, and 

 might be depended upon in the determination of their orders, genera 

 and species, — an inqviiry from which fossil botany and investigations 

 relative to timber were likely to derive advantage. After detading 

 the general structure of the wood-cells of Coniferse, and pointing out 

 peciJiarities that occurred in various plants of the order, he described a 

 remarkable modification which had been noticed in the Yew, viz. the 

 presence in the wood-cell of what appeared to be a spiral fibre, but which 

 had been shown by Harting to be a connected pellicle with thickened 

 ridges arranged in a spiral manner. Mr. Lawson had found this 

 structure to be by no means so rare as had been supposed, and although 

 principally confined to plants belonging to Taxaceae, it was stated not 

 to be universal in that order, nor peculiar to it. He had observed 

 it in the following plants : — Cephalotaxus Fortuni, C. pedunculata, 

 C. tardive, Torreya taxifolia, T. nucifera, Taxus baccata, T. cana- 

 densis, Podocarpus japonica, P. koraiana, Abies Douglasii, Fitzroya 

 patagonica. It also occurred in a specimen of pine wood from Upper 

 California, which presented interesting microscopical characters, but 

 which he had been unable as yet to identify. This structure was not 

 to be confounded with the faint spiral streaks seen under a high power 

 on the secondary membrane of the wood-cells of many Coniferse. It 

 had been long a question whether true punctated tissue was strictly 

 confined to Gymnogens. A careful examination of Drimys grana- 

 tensis and other plants had led him to believe that the disks which 

 occurred in aromatic trees were essentially the same as those of 

 Coniferae, and indeed accorded in a remarkable manner with those 

 of many Araucarise and Taxacese, in which the central dot was not 

 circular) but formed by two elliptical slits crossing each other. The 

 manner in which this appearance aro§e was fully explained bya reference 

 to the spiral arrangement of the slits, which also seemed to account 

 for the alternation of the disks in Araricaria. In the determination of 

 fossil plants and of unknown timbers, Mr. Lawson beheved that 

 valuable characters were afforded by the peculiarities of the wood- 

 cell, such as its general size, presence or absence of a spiral tertiary 

 membrane, arrangement of disks (alternate or opposite), their distance 

 from each other in different directions, and whether in single, double, 

 treble, or quadruple rows on each cell ; absolute size of the disc, and 

 its breadth as compared with that of the cell ; form of disc, whether 

 circular, elliptical or angular, or a combination of these forms ; form 

 of central dot, and (if not circular) direction of the same. The cells 

 of the medullary rays, and the pits in connection with them also 

 afforded useful marks of distinction. By aid of the above characters, 

 to which many more might be added, he had been able to mark di- 

 stinctions between timbers whose appearances to the naked eye pre- 

 sented no definite characters. It was of great importance, however, in 

 adopting such distinctions, that we should also retain the other means 

 of investigation we possess, and his present attempt was meant not to 

 displace, but to supplement these. He is still engaged in the prose- 

 cution of the subject, and expressed an anxiety to obtain additional 



