Why do cycad trunks have an armourlike outer surface?

The trunks of most arborescent cycads are covered in an armourlike surface composed of the hardened, persistent bases of leaves and cataphylls. These stiff, scalelike cataphylls are produced alongside the plant's normal photosynthetic leaves and contribute significantly to this protective outer layer.12

While this exterior provides a durable, armourlike appearance, the internal structure of the cycadophyte stem is notably different; it is relatively soft and fleshy, characterized by a large pith, a thick parenchymatous cortex, and only a limited amount of woody tissue.12