The bare branches of the deciduous trees and brown, decaying plant matter make midwinter feel very bleak, but there are still plants growing, including one that is purported to be the most abundant organism on the planet. The tiny green single-celled alga, Pleurococcus, grows all year round - there is probably some established on your narrowboat. Thriving in moist conditions, it is commonly found on the bark of deciduous trees, more abundantly near the ground on the north side. It spreads up in the wan winter sunlight to dust the bare limbs with a thin emerald sheen. The more acidic surfaces of conifers are avoided, but you will also find it growing on stones, fences and lock gates. The closest relatives of Pleurococcus live in freshwater, but there is fossil evidence of algal mats living on land from over half a billion years ago. Many organisms evolved once they had a foothold on land to give us the diversity of plants today, but the ancestor of Pleurococcus has changed very little.
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