About Limacella
Limacella cf. illinita sensu auct. amer (first image) and L. glischra (Morgan) Murrill
Photographs by RET.
Species of the genus
Limacella Earle (Earle
1909) are strongly differentiated
from the genus
Amanita by their mode of
basidiome
(fruiting body) development (
ontogeny). Whereas the
species of
Amanita share the unique form of ontogeny that is
called “schizohymenial” (see
About
Amanita), basidiome development in
Limacella is generally
like that of all other
terrestrial (ground-growing) Agaricales
in exhibiting the following stages:
-
growth of a minute, vertically oriented, rudimentary stipe (stem)
-
initiation of pileus (cap) growth at the top of the rudimentary stipe [In cross-section, the rudimentary pileus expands at first by extending its edge outward, then downward, and then into a self-enclosing spiral.]
-
initiation of lamella (gill) growth on the underside of the developing cap (the inside of the cap-edge spiral).
In other words, for the species that have been investigated, the lamellae of a
Limacella grow into empty space from the under surface of the developing pileus. As a result, unlike the species of
Amanita, limacellas have a
fertile edge on their lamellae—basidia appear
on the faces and on the edge of a
Limacella lamella.
A fertile gill edge of a specimen belonging to the Amanitaceae is demonstration that the organism in question produced this gill on a fruiting body that did not arise through schizohymenial ontogeny—the gill edge did not have to be separated mechanically from a partial veil or a stipe of an Amanita basidiome. Hence, when the gill edge of a specimen of the Amanitaceae is fertile, that specimen is a Limacella, not an Amanita.
On the cap of a
Limacella, the analog of the universal veil of
Amanita is a
glutinous (slimy) matrix supported by tightly packed,
vertically oriented hyphae (sometimes with distinctive tip cells) that
arise not from a
pileipellis (cuticle or cap skin), but from a dense
layer in the uppermost part of the
pileus context (cap flesh).
Indeed, as in most taxa of
Amanita [sect.
Lepidella]
subsect.
Vittadiniae there is no pileipellis present in
Limacella.
In the literature, a reference to a "pileipellis" in
Limacella
is a reference to the vertically oriented hyphae and associated
slime or
gluten that are the
analog of the universal veil in
Amanita. In the pages of
this site, we will call this structure the
gluten layer of
the pileus or the
"universal veil analog" in descriptions of species of
Limacella. The vertically oriented hyphae in the
gluten layer
will be called the "
gluten retaining hyphae."
What do we know about the gluten layer in
Limacella?
According to the work of Reijnders
(
1979), it develops in at
least two stages:
In the first stage, very narrow hyphae grow vertically from the
outer surface (eventually, the upper surface) of the developing
pileus. These hyphae soon begin to gelatinize and collapse
creating a slimy covering for the immature cap.
A second set of hyphae (of larger diameter than the first group)
develops from the tissue just below the bases of the first set of
vertically aligned hyphae. The second set of hyphae is also
vertically aligned and very tightly packed and carry the previously
created slime upward on their closely packed tips.
The tip (terminal) cells of these hyphae take on shapes that
fall approximately into three groups that (given present knowledge) are
considered as a possible foundation for a hypothetical division of the
genus Limacella into three groups which are given the rank of
sections on this site (until we learn a reason to change this
rank). These sections will be discussed further on the page
titled Sections of Limacella.
With regard to the “slimy partial veil” seen in some species of Limacella, this structure is thought to be a remnant of the development of the universal veil.
Since the young cap has its edges curled under (putting part of the cap surface near to the surface of the developing stipe) some hyphae form wispy (spiderweb-like or cortina-like) connections between the cap and the stipe. These hyphae gelatinize and create a slimy partial-veil-like structure that will include some hyphae. When the cap unfurls and breaks the tenuous connection with the stipe, small tufts of broken hyphae covered with slime may be left encircling a narrow region on the upper stipe. The resulting ring of material looks like a partial veil in Amanita and may be protective of the maturing lamellae for a short time; but its origin and development differ from the origin and development of the partial veil in the schizohymenial genus Amanita.
A membranous partial veil is present in some species of
Limacella—those few comprising
Limacella section Amanitellae.
The state of understanding of
Limacella is behind that of the genus
Amanita. Methodology and terminology have not been as thoroughly developed in the case of
Limacella as they have for
Amanita. The last attempt at revision for North America was published in 1945—sixty-five years before this sentence was drafted. As a consequence, revisions of all type collections and many more recent, well-documented collections will have to be made to gain a better, worldwide grasp of the diversity, taxonomy, and systematics of this genus.
Part of the reason for the lack of understanding is lack of subject matter experts using modern methologies. Lack of expertise may be due, at least in part, to the very small number of collections that exist to support research. This site lists about 50 taxa or probable taxa in
Lepidella, and there are a few pairs or triplets of "taxa or probable taxa" that probably consist of material of a single taxon.
There is a very significant role to be played by disciplined collectors who collect carefully, annotate thoroughly, and photograph well. So few collections of
Limacella are reported each year (e.g., on
mushroomobserver.org or blogs of mushrooming groups) that it is a shame not to have more of them documented more thoroughly and dried well for deposit in a working herbarium that is accessible to specialists. The way to make progress certainly must involve soliciting quality collections from as broad an audience of potential collectors as possible.
The type species of
Limacella is
Agaricus delicatus Fr. : Fr. (1821).
To start exploring
Limacella with an alphabetized directory of the taxa included on this site, go
here.
The images on this page are the work of RET and represent taxa from the Chiricahua Mountains of SE Arizona, U.S.A.
[
NB: Images and well-documented dried collections of
Limacella are sought by both editors.]
