From its response to various chemical, physical, fungal, and enzymatic treatments, it was concluded that the warty layer in balsam fir consisted largely of a ligninlike material that was visibly more resistant to extraction than a large fraction of other lignin in the fiber cell wall. Since the warts were the cell-wall component most accessible to the treatment solutions, it is probable that the material in the warty layer was more concentrated and condensed than lignin in other parts of the wall. Vacuum drying at 105 C appeared to condense the wart structure still further, making it even more resistant to most treatments. Gel filtration indicated that the warty layer was extracted as a high molecular weight material by certain treatments. The warty layer may act as a barrier that slows the penetration of liquids into the cell wall and thereby may cause different rates of delignification for different wood species. The basal component of individual warts and some of the accompanying encrustant on the inner surface of the cell wall were found to contain an amorphous carbohydrate, probably a pentosan or a pectic substance. Attempts at physical isolation of the warts were largely unsuccessful
