In this article we will discuss about the classification of lower fungi.
The modern mycologists consider that the class Phycomycetes is not a natural group of closely related forms. Numerous new proposals for regrouping them are thus forthcoming. Sparrow (1958-59) suggested that the order Plasmodiophorales which includes the endoparasitic slime molds should be given the rank of a class Plasmodiophoromycetes coordinate with the other four classes of fungi.
He thus divided the true fungi into five classes namely, Plasmodiophoromycetes, Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes.
The rest of the Phycomycetes, he classified, on the basis of presence or absence of motile cells in the life cycle and the kind, Number and arrangement of flagella on the motile cells, as follows:
Hawker (1967) supported Sparrow’s suggestion and presented his own scheme of classification of Lower Fungi (Phycomycetes) with slight modifications.
He divided the Lower Fungi into three groups as follows:
Group A. Uniflagellatae:
It includes three classes:
1. Class Chytridiomycetes (motile cells posteriorly uniflagellate) with three orders, Chytridiales, Blastocladiales and Monoblepharidales.
2. Class Hyphochytridiomycetes (motile cells anteriorly uniflagellate) including a single order Hyphochytridia les.
3. Class Plasmodiophoromycetes (motile cells with anteriorly inserted one long flagellum and another very short flagellum) (both whiplash type) including a single order Plasmodiophorales.
Group B. Biflagellatae:
(motile cells biflagellate, one flagellum of whiplash type and the other tinsel type) including one class.
4. Class Oomycetes with four orders, namely, Saprolegniales, Leptomitales, Lagenidiales and Peronosporales.
Group C. Aplanatae (motile cells absent) including two classes:
5. Class Zygomycetes with three orders, Mucorales, Entomophthorales, and Zoopagales.
6. Class Trichomycetes with five orders, Amoebidiales, Eccrinales, Harpellales, Genistellales and Asellariales.
Ainsworth (1973) classified the lower fungi into two subdivisions namely Mastigomycotina and Zygomycotina. Subdivision Mastigomycotina, characterised by the presence of motile stages in the life cycle, has been classified into four classes: Chytridiomycetes, Hyphochytridiomycetes, Plasmodiophoromycetes and Oomycetes.
Subdivision Zygomycotina, characterised by the complete absence of motile stages, has been classified into two classes—Zygomycetes and Trichomycetes.
In this book the system of classification of lower fungi—Phycomycetes as proposed by Alexopoulos (1979) has been followed.