Light micrograph of mnium hornum, a type of moss, showing sex organs. Shown here is a vertical section of a rosette on a male gametophyte. The leafy plant is the haploid gametophyte, bearing male and female sex organs at the apex. The diploid sporophyte is the seta (stalk) and capsule which grow attached to the gametophyte after fertilization. The young capsule is covered by a papery calyptra. The mature capsule opens at its tip by a peristome to shed spores. Moss species are important markers of habitat types. Magnification x12.5 @ 6x7cm.