phellogen

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. See cork cambium.

Century Dictionary and Cyclopedia

1. n. Corkmeristem, or cork-cambium; the inner layers of cork-tissue, which possess cellular activity and give rise to cork.

Wiktionary

1. n. botany The tissue of young cells that produces cork cambium.

GNU Webster's 1913

1. n. (Bot.) The tissue of young cells which produces cork cells.