How are rock-growing ferns adapted to dry conditions?

Rock-growing (epipetric) ferns have evolved several structural and reproductive adaptations to survive in dry, rocky environments:

• Structural Adaptations: These ferns often possess hard tissues and a thick, waxy cuticle on their surface cells to prevent water loss. They may also feature abundant scales or trichomes (plant hairs) on their leaves and stems, which help retain moisture.1
• Reproductive Strategies: Many ferns inhabiting dry rocky slopes utilize a modified life cycle known as apogamy, which bypasses the need for fertilization. This allows for rapid reproduction during brief damp periods, as the gametophyte can develop directly into a sporophyte without requiring free water for swimming sperm.1
• Microhabitat Selection: Even species that tolerate drought typically require specific microenvironments for their gametophytes to develop. On rocks, these gametophytes are usually found in protected crevices where moisture is maximized and light is minimal.1