Scanning electron micrograph of a leaf skeleton of common ivy, Hedera helix. The picture shows part of a shed leaf after several months of decomposition beneath a hedge. The branching vertical structure is part of the midrib of the leaf, about 0.4mm wide. A network of thinner veins remains, but the finest veins, and all the green tissues, have decomposed. Decomposition begins as small invertebrates - woodlice, mites and springtails - eat the soft tissues, or reduce them to fragments that can be degraded by bacteria and fungi. The walls of the leaf veins here - vascular cells (xylem and phloem) that carried water and sugar to and from the leaf - contain lignin. Lignin is a complex polymer that resists chemical breakdown, but even lignin cannot withstand those fungi evolved to degrade it. In only a few more months, the leaf will have been completely recycled back to soil under the hedge.