Dear Andrew, filamentous fungi are those fungi that their thalli are thread-shaped or as described by dear Mr. Dr. Johannes, they are hyphal or mycelial in form. Fungi like species in the genera Mucor (Zygomycota), Candida, Taphrina (Ascomycota), Filobasidium (Basidiomycota) etc are called dimorphic, ie dependent on the medium they grow in, they take one of two morphologies either hyphal (filamentous) or yeast form. Agaricales are filamentous fungi as they grow as hyphae and they have hyphal structures. To be a filamentous fungus is the state of fungal growth. The state of growth is affected by environmental factors like sugars, respiratory gases, pH, and temperature and not so directly related to phylogeny. Dimorphic fungal species indicate both states.

Definitely yes. Mushrooms are mycelial organisms, built up by hyphae. Hyphae are filamentous by definition. Are there arguments against this among your colleagues? Just let me know, why you are in doubt.

Best wishes.

Filamentous fungi are those producing (growing as) true hyphae / mycelium. The definition is sometimes tricky since some taxa have both filamentous and yeast-like stages in their life cycle, being thus dimorphic. To my knowledge, none of Agaricales produce a yeast-like stage. Thus, you can characterize Agaricales as "filamentous fungi". From the taxonomic point of view, the term "filamentous fungi" might be as weird as "yeasts" and include phylogenetically unrelated taxa, like molds and mushrooms.

Dear Andrew, filamentous fungi are those fungi that their thalli are thread-shaped or as described by dear Mr. Dr. Johannes, they are hyphal or mycelial in form. Fungi like species in the genera Mucor (Zygomycota), Candida, Taphrina (Ascomycota), Filobasidium (Basidiomycota) etc are called dimorphic, ie dependent on the medium they grow in, they take one of two morphologies either hyphal (filamentous) or yeast form. Agaricales are filamentous fungi as they grow as hyphae and they have hyphal structures. To be a filamentous fungus is the state of fungal growth. The state of growth is affected by environmental factors like sugars, respiratory gases, pH, and temperature and not so directly related to phylogeny. Dimorphic fungal species indicate both states.

@ Babak, I was not the one asking what filamentous fungi are :)

... and I cannot imagine any strong argument against considering Agaricales as filamentous fungi.

@ dear Andrej, Sorry I mistook You as the asking Person, dear Fang.

Dear Fang, thank You for your kind voting up.

I definitly agree with Andrey and Babak! In fact we could ascertain at least three states of growth in fungi: unicellular (non-yeast; non-filamentous), typically in Microsporidiomycota; yeast-like (many representatives in zygomycetous fungi and Ascomycota; some in Basidiomycota); and filamentous-like that prevails in fungi. These terms are physiological, NOT taxonomic! The Agaricales is presently known to occur in natural conditions only in filamentous state.

Dear Fang Liu. Definitely you can call Agaricales as filamentous. Read Introductory Mycology by Constantine John Alexopoulos. This is a very useful book to understand fungi.