It’s always a bit sad to see the old giants breaking down but this fallen arm provides a view into the interior life of the saguaro. On the outside is the familiar waxy skin tinted green by chlorophyll. Light for photosynthesis is ever-abundant in the desert but rainfall is not, so filling most of the interior is a spongy material where water is converted and stored. Storing water is one thing, supporting its weight is another, a burden borne by the wooden skeleton that runs the length of the saguaro, shown here as broken ribs that shattered as the arm fell from the body.
The saguaro itself still looked healthy to my novice eyes, it will seal off the wound and might well outlive me despite having a head start of two or three of my lifetimes.