Imagine if the tree had a symbiotic relationship with yeast. A developing fruit would have a rind with a semipermeable membrane that performs reverse osmosis on fermenting sugar water within the rind. The alcohol content in the outer chamber of the rind would rise as the fruit developed eventually becoming highly flammable. Eventually, an outer transparent skin on the rind would develop fluid blisters that would act like magnifying glasses focusing sunlight onto the highly flammable alcohol layer. 642
When the developing fruit finally bursts into flame, the outer rind would burn off forming a caramelized shell around the sugar center.
After the mature fruit falls yeast in the fruit's stem would kickstart fermentation in the core of the fruit (separate from the flesh of the fruit...which is of course pure sugar). Alcohol would accumulate in the core in a similar fashion to the rind, but the heat generated by the fermentation process would accumulate in the highly insulated fruit and could eventually result in a nice ethanol explosion.
Now while the tree itself has evolved to be fairly flame resistant to catching on fire, the periodic exposure to brief bursts of extreme heat from its fruit means the tree needs a way to shunt excess heat in its leaves and branches for brief periods of time to avoid bursting into an alcohol-fueled inferno when its fruit ripens. To facilitate this the tree has heat sensitive cells that cause the capillaries in the roots to contract pushing cool pure water from underground up into the leaves and causing the fermented sap in the leaves to be forced back down the tree to the outer skin of the roots and into surface nodules in the root system. These root nodules further cool the tree via evaporative cooling as the alcohol in the sap evaporates through the skin of the nodules.
While the rapid cooling mechanism employed by the root system does work to quickly cool the tree the alcohol vapors released by the root nodules means that occasionally a spark from a ripening fruit will drop into the vapor cloud surrounding the roots catching the vapors on fire. This has been known to light the stems of fallen fruit in the vicinity of the roots which works like a wick causing the alcohol reservoir in the fruit's core to light on fire and explode. 642