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plants and of unknown timbers, Mr. Lawson believed 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 disk, and its 
breadth as compared with that of the cell; form of disk, whether cir- 
cular, 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 connexion with them, also afford 
useful marks of distinction. By aid of the above characters, to 
which many more might be added, Mr. Lawson had been able to 
mark distinctions between timbers, whose appearances to the naked 
eye presented 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 prosecution of the subject, and expressed an anxiety to obtain 
additional specimens for examination. The paper was illustrated by 
drawings and by specimens under the microscope. Specimens of 
timber were also exhibited, including Wellingtonia gigantea, which 
Messrs. Veitch, of Chelsea, had kindly sent through Mr. Evans; 
under the microscope it presented a double row of opposite disks, 
which, as well as their central dot, were elliptical. 
For materials to work upon, Mr. Lawson expressed his great 
obligations to Professor Balfour, Mr. M‘Nab, Mr. Evans, and Mr. P. 
S. Robertson. 
Ophioglossum lusitanicum. 
‘On Ophioglossum lusitanicum, Linneus. By Thomas Moore, 
Ksq., F.L.S. 
The author remarked :—“ The discovery of the Ophioglossum lusi- 
tanicum, Z., within the politico-geographical limits of Great Britain, 
so soon after that of Gymnogramma leptophylla, another South 
European fern, is a fact of much interest ; and I have thought that a 
short account of the plant, drawn up from fresh Guernsey specimens, 
with which I have been favoured by the discoverer, may be of some 
interest to those who are studying either our native ferns or our native 
Flora. 
“ Ophioglossum lusitanicum,. the Portuguese adder’s-tongue, is 
