The provisions of neither convention are obligatory, but merely " facultative," amounting only to recommendations.
Many bacteria may however grow in both the presence or absence of oxygen, and these are termed facultative anaerobes.
The facultative species can be subdivided into primary and secondary facultative ectoparasites.
Many strains are facultative intracellular parasites which produce endotoxins and enterotoxins.
By the latest enactments (one dating from 1905) 2500 citizens can claim a vote ("facultative referendum") as to any legislative project, or can exercise the "right of initiative" as to any such project or as to the revision of the cantonal constitution.