A compilation of yeasts that forms a thick off-white foam on the surface of a wine after fermentation and prevents oxygen from entering the wine. A common characteristic of some styles of sherry. Flor contains four yeasts (sacchromyces beticus, sacchromyces montuliensis, sacchromyces cheresiensis and sacchromyces rouxii) and will not grow on wines that contain over 16.5% abv.