Cellulose is a major component of cell wall of Pythium. Pythium is a genus of parasitic Oomycete. Because this group of organisms were once classified as fungi, they are sometimes still treated as such. Pythium, like others in the family Pythiaceae, are usually characterized by their production of coenocytic hyphae, hyphae without separations. Oogonia generally contain a single oospore. Antheridia contain an elongated and club shaped antheridium.