Horneophyton lignieri: Spores

Spore tetrads of Horneophyton. Diameter of a tetrad is about 70 µm.
The spores of Horneophyton are often still attached to each in so-called tetrads (sets of four).

Spore tetrads of Horneophyton. Diameter of a tetrad is about 70 µm. The spores bear small spines.