Initially, the water flows via capillary pressure into the spongy layer of the epidermis and the porous network of the fern’s leaves, without altering them significantly. Over time, pressure builds up in the fern cell network, changing the turgor pressure and strain in the plant, initiating the unfolding of the leaves. The fern only stops unfolding its leaves when the cell network of the fern is entirely filled with water. The uncurling of the leaves was believed to be an entirely osmotic phenomenon, but when the fern is again exposed to water, it absorbs the water through solid colloids causing an increase in volume and capillary pressure of the cells of the fern. When the fronds "dry", they curl with their bottom sides upwards. In this way, they can rehydrate the quickest when rain comes, as most of the water is absorbed on the underside of the leaf blades. The fern fronds contain canal cells in the center of their surface scales that direct water to the epidermis of the fern leaves, allowing absorption. The ability of the fern fronds to unroll after exposure to desiccation is attributed to the large cells of the upper epidermis along the midrib of the frond that increase in width more than any other epidermal cell, which forces the fronds to uncurl and flatten out. One way the resurrection fern has adapted to survive desiccation is the ability of its cell walls to deform and reform, without bursting or rupturing. It has been observed that dehydrins may allow the cell walls of the fern fronds and leaves to deform and reform in times of extreme drought followed by water exposure, due to large fluctuations in water content. Dehydrins were found to be only expressed when the fern was drying or in the desiccated state, with the dehydrins located on the outsides of the cells near the cell walls, allowing the leaves and fronds of the ferns to deform and reform accordingly. Thermoluminescence of the resurrection fern has been tested to observe at what temperatures it occurs and therefore shows what temperatures and amount of desiccation the ferns can tolerate before their chloroplasts lose the energy they’ve stored for the plant, in the form of light emissions. One study found the resurrection fern to require high temperatures before thermoluminescence occurred at around 50 degrees C whereas other desiccation-tolerant plants showed thermoluminescence at 40 degrees C.