(c) : Ulothrix belongs to Class Chlorophyceae of Division Thallophyta. The plant body consists of an unbranched filament, consisting of numerous cylindrical cells joined end to end. It is heterothallic and sexual reproduction is of isogamous type. Except holdfast each cell of the filament can give rise to 64 to 128 gametes. The gametes are similar in size, shape and other features. So these gametes are called isogametes. When two gametes of (+) and (−) strain come together they fuse and a quadriflagellate zygospore is formed.