VAUCHERIA

genus of yellow-green algae characterized by oil food reserves and multinucleate tubular branches lacking cross walls except in association with reproductive organs or an injury. Asexual reproduction is by motile zoospores and nonmotile aplanospores; sexual reproduction also occurs. The spherical female sex organ (oogonium) and the slender hook-shaped male sex organ (antheridium) are usually produced on branches close to each other. After the nonmotile egg is fertilized by a biflagellate sperm, the zygote may enter a resting phase for several weeks before germinating into a new plant. Although most species occur in fresh water or are terrestrial, some are marine and others live in ice.