1847.] Remarks 07i the Structure of Wood. 285 



beings, and which for the time overcomes it. One remarkable 

 distinction which may be observed in the operations of those two 

 forces is, that the former produces angular, and the latter curved 

 forms, or a tendency to curved forms. It is not my purpose how- 

 ever to dwell upon these well known facts. The doctrine which I 

 wish to state is, that the internal structure of all organized beings is 

 the same in the same species, and if determined, may be employ- 

 ed as a means for distinguishing them. I have already referred 

 to the use which is made of the structure of teeth, and ivory, and 

 also bone, for the discrimination of species in the animal king- 

 dom; so it is believed that the structure of vegetables, may be 

 employed more effectually than it has hitherto been for the cor- 

 rect determination of species. Structure too, it may not be out 

 of place to say, has been employed as the basis of the most phi- 

 losophical methods of classification. It is upon characters which 

 depend upon, or such as are derived from structure, that we dis- 

 cover the most intimate relationship. Though the external form 

 depends upon structure, still it stands only in the second place to it in 

 importance. The structure as developed by dissection must always 

 occupy the first, and furnish the basis for all arrangements which 

 can claim a title to the natural, or that founded upon resemblance. 

 It is often difficult by the ordinary mode of examination to deter- 

 mine the relationship of beings; if however our proceeding is di- 

 rected to their structure, our conclusions can scarcely fail of secur- 

 ing the end we seek. The nearer the structure of individuals ap- 

 proach each other, the nearer will be their relationship; and vice 

 versa, the nearer the relationship, the closer will they resemble 

 each other in their structure. In studying the species composing 

 a genus it is often iound, that two species belonging to it, depart 

 farther from each in structure than two other species of the same 

 genus, and the species of some genera are altogether more natural 

 than the species of another genera. This is easily shown in many 

 instances of forest and fruit trees. In some, the structure seems al- 

 most identical, differing only perhaps in the size of elementai-y 

 parts, while their arrangement is so close that points of distinc- 

 tion cannot be fairly made out. In other species the differences 

 are so obvious that by a glance of the eye we are able to discover 

 them. In the former, the affinity without doubt is much closer 

 than in the latter. 



In trees and shrubs little attention has hitherto been given to the 

 arrangement of the elementary parts which make up the stem or 

 trunk. In exogens the annual layers and the medullary rays, the 

 vessels, etc., have been described in almost every botanical treatise, 

 but in describing their arrangement all trees and shrubs are spoken 

 of as though a perfect similarity every where prevailed; but it is 

 supposed that such diversity exists that the characters which may 



Vol. v., No. 13. 20 



