(from follic, a bag), a species of seed-vessel first mentioned by Linnæus in his Deliciæ plantæ, generally consisting of one valve, which opens from bottom to top on one side, and has no future for falling or attaching the seeds within it.

Folliculi are likewise defined by the same author to be small glandular vessels distended with air, which appear on the surface of some plants; as at the root of water-milfoil, and on the leaves of alderwanda. In the former, the vessels in question are roundish, and furnished with an appearance like two horns; in the latter, pot-shaped and semi-circular.