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The gum ducts are induced in the wood of Azadirachta indica by mechanical injury. The initiation and widening of the ducts are lysigenous. The initiation of the duct takes place with the degeneration of the immediate cambial derivative near the site of injury. The initial shows higher succinate dehydrogenase and acid phosphatase activities than the surrounding cells. The epithelial cells first become secretory and then enter into a phase of senescence and disintegration. Both Golgi bodies and ER appear to be involved in the secretion of the gum. The secreted substance accumulates between the plasmalemma and cell wall. The autolysing epithelial cells show many autophagic vesicles and darkening of cytoplasm preceding their degeneration. The cell wall separation and degeneration progress through the middle lamella from the duct lumen or from the comers of the cells. Disorganised cytoplasm and remnants of cell wall material are observed in the duct lumen.

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