A seed library is an institution that lends or shares seed. It is distinguished from a seedbank in that the main purpose is not to store or hold germplasm or seeds against possible destruction, but to disseminate them to the public which preserves the shared plant varieties through propagation and further sharing of seed. Seed libraries usually maintain their collections through donations from members. but may also operate as pure charity operations intent on serving gardeners and farmers. A common attribute of many seed libraries is to preserve agricultural biodiversity by focusing on rare, local, and heirloom seed varieties.