The perispore is a thin, translucent outer layer forming a sheath or envelope around smooth or ornamented spores. The perispore is also called the perisporium or the myxosporium.

Choose this state if: a partial or complete perispore is visible on spores. The perisporium may be somewhat to distinctly loose in places or all around the spore. Where the perispore forms a partial envelope around the spore it is called calyptrate; where the perispore forms a complete envelope around the spore it is called utriculate. In calyptrate spores, the perispore sits around the apical end of the spore, and is often loosest around the exposed edge. Where spores are ornamented, the perispore may closely follow the spore ornamentation, appearing as a line around the outside of the spore with the ornamentation in the space between the body of the spore and the perispore.