This fern had grown wild in my pots at some point in time.

This fern is well known as a hyperaccumulator of arsenic [1-3]. There are plenty of reports on this property because it present a unique opportunity to utilise the fern as a biological agent to remove excessive arsenic from the environment such as soil or water contaminated with this chemical compound. The process for such utilisation in general are called either phytoremediation or bioremediation.

As for the fern, doing so appears to be a protective mechanism to deter the grasshoppers from feeding on its leaves (fronds) [4].

References:

[1] Xie QE, Yan XL, Liao XY, Li X. The arsenic hyperaccumulator fern Pteris vittata L. Environ Sci Technol 2009;43(22):8488-95. | Abstract |

[2] Tu C, Ma LQ, Bondada B. Arsenic accumulation in the hyperaccumulator Chinese brake and its utilization potential for phytoremediation. J Environ Qual 2002;31(5):1671-5. | Abstract |

[3] Ma LQ, Komari KM, Tu C, Ahang CW, Cai Y, Kennelly ED. A fern that hyperaccumulated arsenic. Nature 2001;409:579-580. | Abstract |

[4] Rathinasabapathi B, Rangasamy M, Froeba J, Cherry RH, McAuslane HJ, Capinera JL, Srivastava M, Ma LQ. Arsenic hyperaccumulation in the Chinese brake fern (Pteris vittata) deters grasshopper (Schistocerca americana) herbivory. New Phytol 2007;175(2):363-9. | Abstract |

Online Resources:

| Flora of China | Ferns of Thailand, Laos and Cambodia | Flora of New South Wales |