Mist sweeps across the valley, swirling around the treetops. Yet, it is a small light beneath the beech canopy that draws my attention, where dense mosses cloak a tree stump. The mosses are careful neighbours, each species taking its own portion of the bark. The deeper tones of Polytrichum formosum, bank haircap, border the lighter Hypnum cupressiforme, Cypress-leaved plait-moss. The former’s darker, pointed leaves make its neighbour’s shiny shoots all the more pronounced. Looking up from these variations in green, a fat raindrop lands in my eye. After the shock of the intrusion, I open it again and turn it back to the mosses. It feels cleansed: as after a spritz of ethanol across a microscope lens, I am seeing more clearly. The rain is also changing the moss. Water lands on the leaves and on the tips of scattered sporophytes – slender shoots topped by capsules containing spores. Tiny raindrops settle on the capsules like a sprinkling of glitter. The shivering sound of rain through the beech leaves at first appears at odds with the seemingly silent, slow-growing mosses. Yet, in the absence of roots, the moss leaves are busy taking in water. While it would take more than a flushing with rain for my eyes to register this microscopic movement, they do catch a general lightening of the leaves. In the darkness, things are shifting. There is a brightening and a lifting. Lumps of flint glint through the leaf litter – silver, white and shimmering. Moss glows from the bottom of the rock. In the Mojave desert in California, botanists have found moss growing under translucent quartz stones, where it is protected from the extreme temperatures and ultraviolet light. Here, the sun is dimmer and rarer, caught only in flashes through gaps in the canopy and rainfall. Still more slight is the light of the mosses. In small waves of green, they operate on a frequency of their own – lower than ultraviolet rays, lower than where the human eye typically strays, but, once tuned into, completely absorbing. Country diary is on Twitter/X at @gdncountrydiary Under the Changing Skies: The Best of the Guardian’s Country Diary, 2018-2024 is published by Guardian Faber; order at guardianbookshop.com and get a 15% discount