The plants form shrubs up to 75 cm tall and seem to prefer stony plains and low ridges. Their thick stems (up to 2 cm thick) have a hard skin containing large quantities of resin and wax. This impervious layer is an excellent way of preventing desiccation.
It also means that the stems can be easily ignited to act as a candle or start a fire.
When you have a good look at the first three pictures, you will notice that the spines start out as leaf stalks, which after a while shed the leaf blades and become hard and rigid.
To be continued.