An anatomical examination of five genera of Urticaceae has shown that the cells of Urera and Touchardia used by the early Hawaiians for fiber are actually thick walled branching non-articulated laticifers. At maturity these cells become lignified, a process which begins in younger tissue in Urera than in Touchardia. These are apparently the only laticifers known to have been used as commercial fibers. True fibers are distributed unevenly along different radii of the stems of Neraudia, Boehmeria and Pipturus. This may represent a plant response to external conditions such as prevailing winds and seems analogous to the formation of reaction wood. The bark of Pipturus, when placed in water, exudes large quantities of an adhesive material that was probably as valuable to the aboriginal Hawaiians for cementing layers of tapa together as the fibers were in forming the substance of the tapa. Experiments suggest the usable fibers of Pipturus were apparently extracted from the bark by scraping and probably were never obtained by retting.