Several species of freshwater green algae belonging to the order Zygnematal
es (Spirogyra crassa (Ktz.) Czurda, S. longata (Vauch.) Ktz., and Mougeotia
viridis (Ktz.) Wittr.) were found to have a specific composition of the vo
latile fraction, which confirms an earlier proposal for the existence of tw
o groups in the genus Spirogyra. Antibacterial activity was found in volati
les from S. longata.