Inocybe | Fungi of Western Siberia

Inocybe reisneri Velen. 1920 is another addition to the list of Inocybe section Rimosae from Novosibirsk Akademgorodok. Last August these fibercaps fruited all over Akademgorodok, always near birch (Betula pendula), preferring shaded lawns bordering forest patches, and sides of busy forest trails (Akademgorodok is all about forest trails).Once again, I failed to take decent in situ photos, probably because these fungi were so abundant I kept hoping to find a better-looking group, and fell victim to perfectionism multiplied by absent-mindedness.

Inocybe reisneri. The violet tinge is especially apparent in young fruitbodies

They stand out of the Inocybe crowd thanks to their elegant fruitbodies with subbulbous stipe, shiny silky caps with scattered patches of white velipellis, violet tinge in the upper part of the stipe and in lamellae, and peculiar smell, which I could only describe as fresh and reminiscent of shieldbugs at the same time. The smell was what prevented me from identifying the species quickly, because it required a two-step move: the thing is, the closest species in Funga Nordica and in Kuyper’s 1986 monograph is Inocybe quietiodor, which is very, very similar (apart from the violet tinge), but a key feature in identifying it is its odor, which is said to be the same as “that of Lactarius quietus“. Apparently, Lactarius quietus is a very common milk cap in Europe, and every decent mycologist should know the smell very well. The problem is, it’s mycorrhizal with oak, and there are only a few planted oak trees in Akademgorodok, and no Lactarius quietus under them (at least yet). We had to google up what Lactarius quietus smells like, and learned that it smelled of “shieldbugs and wet laundry“. Bingo! But the violet tinge wasn’t mentioned in any of the sources.

Yesterday, having travelled for over a month and a half, a great book, an English translation of Stangl’s The Genus Inocybe in Bavaria (available from Summerfield Books), finally made it to Ugut (parcels sent to Russia often deserve their own versions of “The Incredible Journey”). I found our mystery species right away just by flipping through color plates, and it was Inocybe reisneri. A reminder of how important a good library is.

Spores

Spores measure (9.3-) 9.5 – 12.2 (-12.7) x 5.7 – 7.1 (-7.4), L = 9.88, W = 6.26, Q = 1.58 (n = 92), which makes them a bit larger than what’s given in Stangl’s description.

Cheilocystidia are mostly clavate (not very narrow, not very broad). Pileipellis is comprised of relatively thin, barely inflated hyphae with a delicate zebroid pattern of golden-brown pigment incrustation (there is intracellular pigment as well).

Cheilocystidia

Above the pileipellis there is a layer of interwoven, thin, colorless, collapsed hyphae – the velipellis. There are quite a few branching, anastomosing refractive hyphae (also called vascular, or oleiferous hyphae) – as I’ve already remarked, the abundance of these hyphae in a fruitbody is probably linked to the intensity of its smell. The stipe surface is almost polished with just a few scattered small fibrils of velar hyphae with uninflated, cylindric terminal elements.

$Cross-section of pileipellis showing velipellis and refractive hyphae$

Cross-section of pileipellis showing velipellis and refractive hyphae

I’ve already mentioned that Akademgorodok is home to all sorts of species of the genus Inocybe, which seem to enjoy human company: many of them show a marked preference for alleys, courtyards, old playgrounds, trails, or grow under small patches of trees between residential houses.

Many of these (sub)urban Inocybes belong to the section Rimosae, which is characterized by fibrillose-rimose (radially split) caps, smooth, amygdaloid to ellipsoid-ovoid spores, lack of thick-walled, crystal-bearing cystidia (metuloids) and dense rows of thin-walled, clavate (club-shaped) to cylindric cheilocystidia along lamella edges which look like whitish “frosting” under lens. Unfortunately, way too often that’s nearly as far as you can get with identifying species of this section, because even microscopic differences are often subtle; it’s hard to be objective about some of the key features; other are evanescent or hard to put into words (such as the strength and unpleasantness of smell, degree of light-brownness and non-yellowness, scarcity of tiny patches of cottony hyphae = velar remnants, and so on).

Despite these deterring complexities I decided to study and sort out the big pile of specimens that’s accumulated over the past few years, including about 20 more or less decently recorded specimens collected last August. Upon initial examination, many of them fail to fit into the available keys seamlessly: a feature or two always stands out. My plan now is to to measure spores and cheilocystidia, look at stipe and pileus surfaces of all specimens, take notes on gross morphology, then to sum it up in tables and see if any patterns and correspondencies emerge.

Meanwhile I’m just enjoying their grayish-brownness.

Here is a curious one. It was a common sight in late summer on areas of dry, semi-barren, compressed soil, such as abandoned lawns, sides of park trails, etc.

It keys out half-heartedly as Inocybe perlata (using the key to the section provided in a 2009 article by Ellen Larsson et al.) based on its robust habit, spore shape and size, and lack of yellow shades in its coloring, but one thing doesn’t fit: fresh fruitbodies had a faint earthy-spermatic smell, but a very strong and surprising smell appeared when I soaked a tiny piece of dry specimen in water. I ended up running around the nature reserve HQ with pincers: – “Here, smell an Inocybe!” – “Ugh, no way!” – “Smell it!” – “Why… well ok…. Cool! Honey!”. The consensus was, the smell was not even real honey-like, but stronger and clearer, rather like cheap artificial honey flavoring.

I’m not sure whether the slight brownish discoloring seen on some parts of the fruitbody is taxonomically relevant.

There are two species in the aforementioned 2009 article that are said to smell like honey – one is Inocybe cookei, which our mushroom is definitely not, and the other is an Inocybe melliolens, described from France. I haven’t found a detailed description of the latter yet, but Google shows images of very similar-looking fungi, e.g. here or here. There is even what looks like thin velar remnants on pileus surface in the second photo, and I also found what appears to be velipellis fragments on the surface of one of the fruitbodies.

However, these fungi seem to have broader (clavate, not cylindric/subcapitate) cheilocystidia (up to 22 μm wide), although I’m not sure that this feature is stable enough to mean much (if it does, then Inocybe maculata appears in the picture).

There are abundant refractive hyphae found throughout the fruitbody, which in my experience correlates directly with smell strength. Here’s a picture of such refractive hyphae in the pileipellis:

The caulocystidioid elements on the stipe (they’re the whitish fuzz) are very typical for species of this section:

Here’s the pileipellis, with rather wide, inflated hyphae:

and the velipellis:

Spores

I guess the only way to get a definitive answer is molecular study: hopefully one day an Inocybe expert becomes interested in Siberian samples….

Fungi of Western Siberia

Tag Archives: Inocybe

ressaure

January 29, 2014

New finds in 2013. 3 – Inocybe sp. (sect. Rimosae)