It's one of nature's ironies that sometimes the seemingly delicate and fragile living things inhabit the most challenging, inhospitable environments. Yet the Slender Fragile Fern (Cystopteris tenuis), also known as Mackay's Brittle Fern, clings to shaded areas on rock faces where one would think it difficult for a plant to survive, let alone flourish.
The dorsal surface ...
... and the underside of a frond.
Closeup views of the sori (spore producing structures).
