In 1921 Smith wrote the illustrated Handbook of British Lichens which was a key to all known British lichens. In the same year Lichens was published and was quickly established as a classic text.
The publication of Smith's "Handbook of British Lichens" in 1921 marked a significant milestone in the study of British lichens, providing a comprehensive guide to their identification. The same year saw the release of "Lichens," which quickly became an essential resource for researchers and enthusiasts alike.