Subkingdom Mastigobionta

Unicellular organisms commonly known as chytrids and water molds belong to this Subkingdom. They are very small motile cells which possess flagella. The orgin of the chytrids is unknown whereas the water molds appear to have been derived from the brown algae.

Division: Chtridiomycota (chyrids)

Tiny unicellular organisms that produce motile cells with a single flagellum.

Order: Blastocladiales

Possess reproductive cells each with a single posterior flagellum; nonseptate hyphae (except gametangia); sporophyte produces two types of sporangia depending on environmental conditions.

Allomyces

Division: Oomycota (water molds)

The water molds possess several features in common with the brown algae: oogamous eggs, cellulosic cell walls, zoospores with two flagella (produced at various stages of their life cycles) and a predominately diploid life cycle.

Order: Saprolegniales

Water molds occurring in mostly freshwater habitats and top layers of moist soils; some cause disease in fish and destroy fish roe in commercial hatcheries; others causes root rot in food crops.

Saprolegnia | Achyla ambisexualis

Order: Peronosporales

Terrestrial fungi; develop their entire life cycle on living hosts and cannot be grown in laboratory culture. Of great economic importance, two of which have had a great impact on human affairs. Both Phytophthora infestans and Plasmopara viticola pass their entire life cycle inside the tissues of their plant hosts and produce sporangia on the host surface.

Phytophora infestans | Plasmopara viticolor