(top) No septate hyphae of the pathogen Pythium debaryanum that form the fungus mycelium. Along the hyphae are develop sporangia that can directly germinate into mycelium or form zoospores that carry infections. (bottom) Oogonia and antheridia, sexual reproduction organs of Pythium debaryanum. After oogonia fertilization, is created spore with thick sheath called permanent spore or oospore that may preserve older the germination. With oospores the pathogen performs the primary infections.