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In this article we will discuss about the classification of phycomycetes.
The Phycomycetes are classified into three subclasses on the basis of their somatic structures, the nature of spores by which they reproduce asexually, and the method and end product of sexual reproduction. The three subclasses are again subdivided into orders and orders into families.
The following is an outline of the key to the subclasses, their respective orders and families:
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A. Mycelium lacking or poorly developed (a rhizomycelium), thallus holocarpic, or eucarpic, sexual reproduction of various kinds, zoospores uniflagellate.
Subclass Archimycetes
B. Mycelium lacking, rhizomycelium present, thallus holocarpic or eucarpic
Order Chytridiales Family Synchytriaceae Genus Synchytrium
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BB. Mycelium present, scanty or profuse; thallus eucarpic
C. Sexual reproductisn by fusion of planogametes, thick-walled resistant sporangia always present
Order Blastocladiales
Family Blastocladiaceae
Genus Allomyces
CC. Sexual reproduction by fusion of a free-swimming male planogamete with a female apalanogamete, resistant sporangia lacking
Order Monoblepharidales
Family Monoblepharidaceae
Genus Monoblepharis
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AA. Mycelium well-developed, thallus eucarpic, reproductive parts separated from assimilatory part by cross-walls
B. Gametangia morphologically distinguishable as male and female, sexual reproduction by gametangial contact with oospore as end product, asexual reproduction by biflagellate zoospores
Subclass Oomycetes
G. Oospheres one to several in each oogonium; periplasm absent; zoospores biflagellate, diplanetic to monoplanetic
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Order Saproleginiales
Family Saprolegniaceae
Genus Saprolegnia
C. Oosphere one in each oogonium; periplasm present; sporangia germiriating by zoospores or germ tube, zoospores biflagellate, monoplanetic, formed within the sporangia or within an evanescent vesicle arising from the sporangium.
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Order Peronosporales
D. Sporangiophores mostly similar to the somatic hyphae or, when different, with indeterminate growth
Family Pythiaceae
Genus Pythium
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Genus Phytophthora
DD. Sporangiophores clearly different from the somatic hyphae with determinate growth; sporangia borne on branched or un-branched sporangiophores, or on various types of sporangiophores.
E. Sporangia in chains on clavate sporangiophores borne in dense sori
Family Albuginaceae
Genus Albugo
EE. Sporangia borne singly or in clusters at the tips of branched or unbranched clavate sporangiophores.
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Family Peronosporaceae
Genus Peronospora
Genus Plasmopara
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BB. Gametangia morphologically not distinguishable as male and female, sexual reproduction by gametangial copulation with zygospore as end product, asexual reproduction by sporangiospores
Subclass Zygomycetes
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C. Saprophytes, some weak parasites, asexual reproduction by sporangiospores formed inside a sporangium, sometimes replaced by sporangiolum
Order Mucorales:
D. Sporangial wall not cutinized, sporangiospores liberated by breaking or dissolution of sporangial wall, suspensors rarely tong-like
Family Mucoraceae
Genus Mucor
DD. Sporangial wall cutinized, sporangium violently discharged or passively separated as a unit from sporangiophore, suspensors always tong-like
Family Pilobolaceae:
Genus Pilobolus
DDD. Sporangium many- to few-spored or replaced by unicellular conidium
Family Choanephoraceae:
Genus Cunninghamella
CC. Parasitic on insects (entomogenous) or saprophytic on insect skins that have been cast, or animal excreta; reproduction asexually by means of violently discharged conidia.
