a little water is present, the fern will uncurl and reopen, appearing to "resurrect". It has been estimated that these plants could last 100 years without water and still revive after a single exposure. The resurrection fern roots have evolved to function as anchors for the epiphytes, holding them to their host tree’s bark and have been found to be inefficient in absorption. When in clustered groups of ferns on the bark of trees, the increased transpiration of the ferns and bark allow the middle ferns of the cluster to remain open longer than ferns on the outside. The relative humidity of the air and the closing rate of the leaves of the ferns is an inverse relationship. The greater the humidity, the slower the leaves of the ferns close because they have prolonged exposure to moisture in the air. The resurrection fern can severely desiccate and lose almost all of its water. Experiments have shown they can lose up to 97%--and remain alive, though more typically they only lose around 76% in dry spells. For comparison, most other plants would die after losing only 8-12%. This fern can lose almost all the water not hydrating the cells in its leaves and survive. Upon rainfall or even minute exposures to water they can fully rehydrate and return to a normal state within 24 to 48 hours. Following substantial exposures to moisture, there is an immediate increase in its water content of up to 50% after the first hour and 65-70% after three hours. When it regains moisture, the fern can once again become photosynthetically active, increasing its metabolism and release of organic compounds that provide nutrients for symbiotic bacteria that allow them both to thrive. At least one study has shown association between P. polypodioides and moss, indicating that this fern may rely on moss for some of its water needs. The resurrection ferns accumulate sugar in their dehydrated cells in order to protect them and stabilize the membranes and proteins in the dry state. By accumulating sugar, the cells can maintain hydrogen bonds between necessary macromolecules needed for their structure. An interesting feature of the resurrection fern is it does not immediately uptake water after having been in a desiccated state. The resurrection ferns have porous cell structure networks that can expand and rearrange to accommodate absorbing three to four times their own weight in water after being exposed.