Saccharomyces is commonly known as the yeast. S. cerevisiae is commonly known as the yeast. The cells are unicellular. The cells are rectangular, oval, and elliptical in outline. The cell wall is made up of chitin. Cellulose is absent. The vacuolated cytoplasm contains oil drops, volutin granules and various organelles like endoplasmic reticulum, ribosomes and dictyosomes. The central vacuole is surrounded by a limiting membrane called as tonoplast. Saccharomyces reproduces by vegetative means i.e. by fission and by budding. It also shows sexual reproduction during unfavorable conditions when the food supply is exhausting. Three types of life cycle are found i.e. Haplo-biontic life cycle , Diplobiontic life cycle, and Haplodiplobiontic life cycle.

Oscillatoria is found in rain water of pools, ponds, rivers, streams, lakes and in polluted water. Some of the species of Oscillatoria are plank tonic, some are found in hot water springs e.g O. terebriformis, and some species of Oscillatoria are found in saline waters. e.g. O. limosa. Oscillatoria in unbranched and filamentous. The trichome consists of cells which are arranged in uniseriate fashion. Oscillatoria species show Gaidukov phenomenon. Species of Oscillatoria can assume different shades when they are provided with light of different wavelengths. The trichome shows gliding movement as well as oscilllatory movement. During vegetative growth of the trichome, some cells of the trichome are filled with mucilage and become dead. These cells are called necridia. Thus Oscillatoria reproduces by the formation of Hormogonia and by fragmentation.