The Oedogoniales are remarkable filamentous green algae. Their method of cell elongation is unique, utilizing a donut-shaped ring of soft wall material which is stretched to form the new daughter cell. While Oedogonium is a simple filament, the related Bulbochaete and Oedocladium are branched and Bulbochaete differentiates long hair cells. The zoospore is large and multiflagellated. Sexual reproduction is oogamous and either "macrandrous" or "nannandrous." Differentiation of oogonia and antheridia is initiated by highly asymmetric cell divisions. Fertilization is rapid and efficient. These aspects of their biology are vividly illustrated in color by time-lapse video microscopy. This video is essential for those who teach phycology and will fascinate anyone who is interested in the way 'simple' cells live and evolve.