It is often possible to identify fragments of plants by studying their microscopical characteristics. The recognition of a single feature very rarely establishes the plant's identity; more often, it is necessary to recognize a unique combination of characteris- tics. For plant identification, the most valuable characteristics are those least likely to be affected by changes in environment; if the feature is uncommon as well as stable, it is even more useful. Good descriptions of the anatomy of plants are invaluable. For example, The Identifi- cation of Hardwoods (Brazier and Franklin, 1961),...