About Amanita


Collage of images of Amanita taxa.
Each image is linked to the taxon page providing a description of the taxon depicted and a credit for the image.


The definition of the genus Amanita has been slightly complicated from a morphological point of view by the inclusion of at least seven species in the genus that are not agaricoid (do not have the form of a typical gilled mushroom with a central stem and have lost the ability to mechanically discharge spores).  Having already place all amanitas in our morphological definition of the Amanitaceae (see About Amanitaceae), our task of defining the genus Amanita is made easier.

The genus Amanita includes all and only those members of the Amanitaceae that produce a fruiting body (basidiome) satisfying exactly one of the following conditions:
  • It is hypogeous (it has lost the ability to mechanically discharge its spores and grows under ground).
  • It is secotioid (it has lost the ability to mechanically discharge its spores and grows above ground) or agaricoid and exhibits the mode of basidiome development (ontogeny) that is called schizohymenial (growing from a solid mass without cavities in which all the parts of the mushroom develop in place and then have to be split apart in final stages of development).
In most of the world this reduces the practical matter of identification of agaricoid specimens of Amanita to the tasks of finding in that specimen the same evidence that has been very clearly required since the publication of the thesis of Dr. Cornelis Bas in 1969.  An agaricoid or secotioid mushroom is an Amanita if and only if you can demonstrate that the specimen
  • has longitudinally acrophysalidic stipe tissue
  • is not a species of Limacella.
If an unopened button of the species is available, and you find that all the developing elements (cap, stem, gills, volva) of a mature mushroom are visible as distinct, shadowy regions in a cross-section of the button and that these developing elements are interconnected by tissue so that there is no open space within the button, then
you have demonstrated that the probable ontogeny of the button is schizohymenial—literally that the faces of adjacent gills must be split apart from each other as the development of the mushroom continues.
If an agaric exhibits schizohymenial development it can only be an Amanita—this ontogeny is restricted entirely to the genus Amanita.  Hence, you don’t have a Limacella.

If the collector of your specimen found no buttons or found them but did not retain them for your edification, then you should view the page About Limacella on which distinctive morphological features of Limacella are described; and you must show that the material you have in hand lacks those distinctive characters.
Here is a simple method of separating dried specimens of Limacella and Amanita with microscopic examination of the gill edge.  Check whether the edge of a gill is fertile (has spore-bearing basidia growing from it) or sterile (doesn't have basidia growing from it).

In the Amanitaceae, the fertile condition occurs only in Limacella.  The sterile condition is found only in Amanita.

The sterile condition can be recognized as follows: In Amanita, the gill edge is comprised of a “cable-like” grouping of hyphae running the length of the gill edge and giving rise to balloon-like cells of various shapes (singly or in short chains) which separate, collapse, gelatinize, and/or break, facilitating the the separation of the gill edge from the stem or from the partial veil (ring, annulus, skirt) as the elements of the expanding Amanita basidiome are separating.
The reader may think, "Surely, I recognize an Amanita when I see one."  In response it must be said that, in many cases (especially with regard to taxa similar to locally familiar taxa), the reader probably does know his/her amanitas by sight.  On the other hand, it still happens that professional mycologists name species in the genus Amanita that are not amanitas.  Wouldn't you like to avoid that happening to you?

The type species of the genus is A. muscaria (L.: Fr.) Lam. [ ≡Agaricus muscarius L. (1753) ].

To start exploring Amanita with an alphabetized directory of the taxa included on this site, go here.

Subgenera

The genus is divided into two subgenera depending on the reaction of spores to an iodine solution (e.g., Melzer's Reagent).  A darkening reaction of a spore's wall to this solution is called an amyloid reaction and lack of such a reaction classifies a spore as inamyloid.

Species having spores producing the amyloid reaction are classified in Amanita subgenus Lepidella.  The type species of this subgenus is A. vittadinii (Moretti) Vitt.  The directory page for this subgenus can be found here.

The species with inamyloid spores are placed in Amanita subgenus Amanita.  The type species for subgenus Amanita is the same species that is the type for genus as a whole—A. muscaria.  For an alphabetized directory of the taxa of subgenus Amanita, go here.

Sections

The subgenera are further divided into sections.  There are seven sections currently recognized in Amanita.  In the pages of this site, sectional names follow the usage of Corner and Bas (1962) and Bas (1969) as emended in Yang (1997).  A description of the sections of the genus can be found here.

[NB: Images and well-documented dried collections of material from outside their respective regional collecting areas are sought by both editors of this site.]