The germ pore is a differentiated area of the spore wall at (or near) the apex where all or some of the individual layers of the wall are interrupted or modified. Overall, when a germ pore is present, the wall at the apex appears thinner and/or paler.

The term 'callus' is sometimes used in contrast to a germ pore for a thin spot, but merely refers to a type of germ pore where the wall at the apex is thinner and not very truncate.

The germ pore is most often at the centre of the apex, but can be off-centre (oblique).

A germ pore is present most often in spores with distinctly thickened walls. For pale or hyaline spores, staining may make the germ pore easier to see.

A thickened, protruding region of the spore wall at the apex is called a papilla, and is a different stucture to a germ pore.

Choose this state if: there is a germ pore, but it is narrow and the outline of the spore is not truncate.