triradiate scar

A scar on the surface of a spore that marks the point at which it was joined to the other three spores making up the tetrad. Triradiate scars are seen when the *tetrad shows tetrahedral symmetry. It is conspicuous because the spore wall is fairly thin at this pont while the rest of the wall is thickened with cutin. In the megaspores of Selaginella krausiana the archegonia break through the megaspore wall at this point. Spores bearing a triradiate scar are termed trilete. See monolete.