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Hemimycena: a difficult genus?

INTRODUCTION
GENERIC CONCEPT
DIAGNOSTIC CHARACTERS

Hemimycena juncicola

Hemimycena pseudocrispula

Many mycologists have difficulties with the identification of Hemimycena
There are different reasons. First of all because most species are small and white and do not show many morphological characters. Often you have to search for microscopical characters to be able to use the existent keys. For this microscopical work you need skill and experience.
During the past decade Vladimír Antonín (Botanical Museum, Brno, Czech Republic) and I have been succesfully cooperating on monographic treatments of white spored agarics. This resulted in two books on marasmioid and collybioid fungi. In 2004 we published our third monograph dedicated on some genera of tribus Myceneae, including Hemimycena.
hemimycena cover

Hemimycena lactea

GENERIC CONCEPT

Habit mycenoid or omphalinoid
Pileus white, rarely tinged yellow, ochre or grey
Stipe centrally inserted or lateral, sometimes reduced
Spores and context inamyloid
Cheilocystidia usually present

DIAGNOSTIC CHARACTERS
Macroscopic characters pileus lamellae stipe smell	Microscopice characters spores cystidia cap cuticle (pileipellis) covering of stipe

		pileus In Hemimycena many different shapes may be encountered. varying from campanulate to conical with a pointed umbo, to semiglobose, convex or depressed to funnel-shaped. Often the margin of the pileus is wavy. The surface usually is not glabrous, but finely pruinose, powdered of hairy.
stipe The stipe is centrally inserted rarely eccentric. The nature of the surface is of great diagnostic value: often rather characteristic cystidia or hairs can be observed. Rarely the stipe surface is smooth and glabrous. see also stipe surfaceunder microscopical characters.		lamellae The lamellae of most species are adnate tot distinctly decurrent on the stipe. Only in a small group the lamellae are ascending to free. A good diagnostic character is the development of the lamellae: fully developed and reaching from the stem to the margin of the cap, or reduced, often vein-like and frequently not reaching the margin of the cap. Rarely the lamellae are (almost) lacking, resulting in a smooth lower surface of the pileus.

Smell

most Hemimycena species do not have a distinct smell. A few of them, however, expose a rather strong and distinct smell of chlorine, also called nitrous.

		Spores Spores may have a rather different shape and size. frequent types are: round (globose) (Q = 1.0-1.1) ovate (Q = 1.3-2.0) pip-shaped fusoid(Q > 2-3)
		cystidia cystidia Cystidia along the edge (cheilocystidia) and on the sides (pleurocystidia) of the lamellae frequently occur. Frequent types are: bottle-shaped (lageniform) irregularly coralloid with short or longer finger-like outgrowths. lecithiform to tibiiform with capitate apex
		covering of stipe (stipitipellis) The cystidia and hairs on the stipe can be rather different. flexuous tot cylindrical with a capitate apex coralloid with short or long finger-like outgrows attenuated with thickened wall (setiform) attenuated with thin walls and often a mucous cap over the tip
		Pileus covering (pileipellis) The pileipellis in Hemimycena usually is a cutis of more or less cylindrical hyphae with few to numerous finger- or wart like outgrows(B). This is called diverticulate. In a few cases the pileipellis consists of short, sowllen cells that are arranged as the basidia in a hymenium. This type is called hymeniderm(A)
		Pileocystidia The hyphae of the pileipellis sometimes bear distinct cystidia. These are often irregularly shaped and coralloid or diverticulate(A) zijn. One group species is characterized by the presence of setiform pileocystidia(B)