Why should the identification of a piece of timber matter? Why should anyone want to know what species of wood has been used for a particular job? Isn't all wood the same - doesn't it just come from trees? The answer to the last question is a resounding NO!
There is no such thing as simply 'wood' which can do everything that you might want it to do.
Some timbers are highly decorative, some are very strong, some have good resistance to rot (whereas some behave very badly when they get wet) - in fact almost every species of wood has features that can be good in some uses, but no so good in others. Therefore, knowing what wood you have in front of you can be extremely important, either because you may have paid a lot of money for something you didn't actually get, or maybe because the wood you've got is unsuitable for the job you have in mind for it.
Timber identification is a skill that must be gained with practice - and with a bit of extra help from a skilled Wood Scientist.
Hardwoods can often be identified simply by means of their larger 'diagnostic features' - using nothing more complicated than a x10 magnification hand lens: whereas Softwoods (with their simpler, but generally harder-to-see cell structure) can often only be identified by putting a thin slice of the wood under a microscope. Either way, getting the right answer - with regard to wood species - is often vital in making sure you have the right timber to do the right job.
Trees are identified by examining the leaves, flowers and fruits of the tree, but in commerce we can only identify wood by examining the anatomy of the solid material. There is often a need to identify timbers when they are being assessed for strength properties in situ. Different timbers have different strength characteristics. Restorers and conservators need to identify timbers so that replacements can be selected. Most timber in the UK is responsibly purchased from sustainable sources, but timber species must sometimes be checked to ensure that endangered species are not being traded.
The microstructure of wood is very beautiful and is often the inspiration for textile and graphic designers.
For identifying wood from broadleaved trees it is often sufficient to make a clean cut with a razor across the end grain and observe features such as the arrangements of vessels that transport water up the tree, the arrangements of rays, growth rings, colour, etc. Sometimes the tangential and radial surfaces must be cut for extra details. In advanced cases, thin sections must be cut for examination under a microscope.
To identify softwoods, microscope equipment is essential. The cellular structure of coniferous timbers is very fine and details such as the fine holes in the cell walls must be characterised. Thin sections, perhaps 25 micrometres thick are cut with a microtome, stained and examined with a microscope capable of up to 400 times magnification. Observations are compared with standard keys.
Note that because a tree is identified by examination of the leaves and flowers, anyone identifying a wood species will often not be able to be categoric. The sample may be one of several closely-related species; so the best that is often possible is something to the effect of: 'From the features observed, they accord well with timber of the genus Prunus'