Brightfield light micrograph of a sporangium of a Bryum sp. moss. The sporangium is terminal stage of the moss sporophyte development. Spores are produced as the result of meiotic divisions of archesporial tissue inside the moss capsule. Some moss capsules are equipped with a single or double ring of tooth-shaped cells (peristome) which are sensitive to humidity. Peristome cells help in the sporangium opening and spore release. Every haploid spore can germinate into a protonema and start a moss gametophyte generation. Magnification: x65 when printed 10x 10 cm.