Light micrograph of a transverse section of a moss (Atrichum undulatum) leaf. Visible are two lateral single layer parts of the leaf blade and a multi-layer midrib part. Four lamellae are growing out of the midrib. The midrib is composed of sclereids, supporting cells with thickened cell walls, and hydroids, which are bigger cells with thin walls that are elements of the leaf conducting system. Magnification: x300 when printed at 10 x 10 cm.