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246 GROWTH PARAMETERS
The Beech Mushrooms
(Bunashimeji and Shirotamogitake) of the Genus HypsizyguS
The rich flavor of the Shimeji mushroom can be summed up by the Japanese phrase "for fragrance,
Matsutake; for flavor, Shimeji". However, the name "Shimeji" is widely used to describe
some of the best Japanese gourmet mushrooms that grow "on wet ground". For years, the general
name Shimeji has been assigned to about 20 mushroom species, causing widespread confusion
amongst amateur and professional mycologists.
Recently, a number of scientific articles have attempted to clarify what is the "true Shimeji" which
the Japanese call Hon-shimeji. (See Clemencon & Moncalvo (1990); Nagasawa &Arita (1988)).The
Hon-shimeji of Japan is actually a Lyophyllum, i. e Lyophyllum shimeji (Kawam.) Hongo. This species
is not commercially cultivated, and according to researchers at the Mori Mushroom Institute,
may even be a mycorrhizal species. * (Motohashi, 1993). The confusion is understandable because
young specimens of Lyophyllum shimeji look very similar to Hypsizygus tessulatus, known in Japan
as Buna-shimeji or the Beech Mushroom.
The Genus Hypsizygus was first described by Rolf Singer and contains two excellent, edible and
choice mushrooms. Collected in the wild by Native Americans (Singer, 1986), these mushrooms are
otherwise not well known to other North Americans. Species in this genus are generally saprophytes,
but can become "facultative parasites" when trees, particularly elms and beeches, are dying from
other diseases. These mushrooms have a tendency to grow high up on the trunks of trees, making the
collecting of wild specimens difficult for the unprepared or unathletic. (Hypsi- means "on high or
aloft" and -zygus means "yoke".) Only two species are known in this Genus, H. tessulatus
(Bull.:Fries) Singer and H. ulmarius
(Bull.:Fries) Redhead. Both cause a brown rot of hardwoods.
Firmer fleshed than most Pleurotus species, Hypsizgus mushrooms out-class the Oyster varieties
commonly cultivated by North American and European growers in terms of flavor and texture. Here
again, the Japanese are credited for first commercially cultivating Hypsizygus. Recent Japanese research
shows that H. tessulatus may be active in retarding tumor growth when consumed. (Ikekawa,
1990). Studies are on-going to more precisely determine their medicinal properties.
The Genus Hypsizygus most closely resembles Lyophyllum and to a lesser degree Pleurotus. These
taxa are separated by the following combination of features. First, Hypsizygus and Pleurotus typically
grow on wood, above ground level. Lyophyllum grows on the ground, in soils rich in woody
debris. Furthermore, Hypsizygus species lack numerous granules within the basidia, a feature that is
characteristic of members in the Genus
Lyophyllurn. (These granules are siderophilous, i.e. the granules
become apparent in acetocarmine, a stain used by mycologists to bring out internal cell features.)
Hypsizygus spores are small, generally less than 7 microns, and more ovoid in shape compared to the
soil microflora for fruitbody formation in the same manner as
Stropharia rugoso-annulata than being a mycorrhizal species.
* I find it more likely that L. shimeji depends upon
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