142 Mr Nicol on the Structure of 



ferior for various architectural purposes to that of many of the 

 true pines. 



On comparing the relative breadth of the partitions with the 

 size of the meshes or openings, in a transverse section of diffe- 

 rent species of Coniferae, we find a very considerable difference. 

 In some, as the Pin us strobus, Pinus canadensis, &c., the lig- 

 neous substance composing the partitions occupies a much 

 smaller space than that of the intermediate meshes. In others, 

 as the Taxus baccata, the ligneous substance composing the 

 partitions occupies a larger space than that of the meshes, and 

 the yew is well known to be greatly superior to any of the pines 

 in strength or tenacity. The differences in question may be 

 seen by inspecting the first and fourth figures of Plate II. I 

 may here observe, that the whole of the sections figured in all 

 the plates were drawn of the sizes as they appeared to the eye, 

 when viewed with a double convex garnet lens of nearly a 

 fortieth of an inch radius. 



The transverse sections of Coniferae present appearances of so 

 much similitude, that it is not very easy in every case to dis- 

 tinguish one species from another, especially in the pine tribe ; 

 but the finer texture might enable an eye familiar with the sub- 

 ject to distinguish the Junipers and Thujas from the Pines, and 

 the irregular form of the meshes in Salisburia and Araucaria 

 might enable one to distinguish them not only from the pines, 

 but also from the Junipers and Thujae. 



Besides the general reticulated texture as seen in the trans- 

 verse section, occasional circular openings of larger dimensions 

 than any of the meshes appear in many of the true pines. They 

 often occur in Pinus strobus, P. sylvestris, P. abies, and P. 

 Larix; but I have not observed them in Pinus picea, nor in P. 

 canadensis, nor in P. cedrus, nor have I ever seen them in the 

 Junipers, the Thujae, the Cypresses, the Salisburia, or in the 

 Araucarias. They are called Lacunae from the circumstance 

 of their appearing empty, especially as seen in very thin trans- 

 verse sections. They are longitudinal tubes, and are complete- 

 ly filled in their whole length with slender membranous sub- 

 stances, which seem to lie in different directions. When a 

 longitudinal section passes through the centre of one of these 



