SYNGENESIS, (gen and genere, "congeneration"), the name of the 16th class in Linnæus's artificial system; comprehending those plants which have the anthers united into a cylinder. The orders are fix: 1. Polygamia æqualis. 2. Polygamia superflua. 3. Polygamia frustranea. 4. Polygamia neccessaria. 5. Polygamia segregata. 6. Monogamia. The five first orders contain the compound flowers, and form a class truly natural.