WordReference Random House Unabridged Dictionary of American English © 2026
pro•to•xy•lem
(prō′tə zī′ləm, -lem),USA pronunciation n. [Bot.]
- Botanythe part of the primary xylem that develops first, consisting of narrow, thin-walled cells.
- proto- + xylem 1895–1900
'protoxylem' also found in these entries (note: many are not synonyms or translations):