An illustration of a pinnule of aspidium showing veins and sori.

Pinnule of Aspidium

An illustration of a pinnule of aspidium showing veins and sori.

An illustration of a pinnule of aspenium showing veins and sori.

Pinnule of Asplenium

An illustration of a pinnule of aspenium showing veins and sori.

"Frond of fern bearing sporangia in sori."—Finley, 1917

Fern frond

"Frond of fern bearing sporangia in sori."—Finley, 1917

An illustration of a pinnule of polypodium showing veins and sori.

Pinnule of Polypodium

An illustration of a pinnule of polypodium showing veins and sori.

An illustration of a pinnule of pteris showing veins and sori.

Pinnule of Pteris

An illustration of a pinnule of pteris showing veins and sori.