The Chestnut Bolete, Gyroporus castaneus

 

Towards the end of the afternoon the Field Club members visiting Pilot's Wood came across a small patch of the Chestnut Bolete, Gyroporus castaneus, in amongst Sweet Chestnut mixed with Oak. This is the first time I have knowingly seen this attractive, inoffensive bolete. 

The group of Gyroporus boletes was moved into this genus sitting in its own family because of their really quite unusual cellular morphological features. This is one of two generally recognised UK species, the other being the Cornflower Bolete, Gyroporus cyanescens, a larger and chunkier bolete that is mycorrhizal with a large range of trees across its widespread range, and has flesh that blues quite intensely and quickly. 

Gyroporus castaneus is a generally light to dark brownish and relatively small bolete with white flesh, and very pleasant smell and taste. Thought to exist in Europe, North America, Asia, Africa and Australasia, in other continents it may perhaps be a species complex, based on DNA evidence. One of its stand-out features, shared with other members of its genus, is the tendency of the stem to become hollowed out, firstly in a number of separate chambers and then often completely. The cap and stipe are dry and the stipe does not have dots or a reticulum. The cap and stipe may be fairly brittle and split spontaneously. The spore colour is a straw-yellow - unusual for the Boletaceae.

The pores may darken when pressed, or with age, sometimes to quite a dark brown, but the flesh does not change colour, for example to blue, when cut. The pores are free from the stem.

Although the specific name is castaneus, the name is for the chestnut-brown colour, not its associated tree, and it is I think more generally found in mycorrhizal association with Oak. The geographical distribution covers all 4 home nations, but it is commonest in the southeast of England. 

These particular caps found in Pilot's Wood are lighter than generally expected, but within the potential range. They are mottled, partly concolourous with the stipe which is lighter in colour at the apex than the base, as quite regularly observed.

Showing the spontaneously appearing hollowed out chambers in the stipe:

 

The Lurid Bolete, Suillelus luridus

At the start of the KFC visit to Pilot's Wood and Meenfield Wood, which is a woodland complex near Badger's Mount and Polhill, and next to the Kent Wildlife Trust's chalk grassland reserve of Polhill Bank, the group quickly came across a very small patch of the quite colourful Lurid Bolete, Suillelus luridus, which I hadn't seen before and we didn't see again that day.   

Initially it looks quite a demure bolete with its overall matt brownish appearance, which I would have described as mainly khaki, with only subtle hints of apricot, in contrast to the book descriptions which rather emphasise the apricot. But looking a bit closer, you see the bright orange-reddish pore surface as well as the strong red reticulum over the yellowish stem and the intense blue when you cut the flesh or bruise the pores, together with a "purplish" base to the cut stem, and the overall impression is of a rather garish bolete! In these specimens the colour of the caps is quite matt, but still shows the apricot tinges of the published descriptions.

However, I failed, critically, to pick up the red colour in the line above the pores, this was clearly present but looked blue to me, but no-one else mentioned it, and the decision was very clear - luridus it was. This is a close-up of the cut surfaces. The patch at the base looked more orange to me rather than purple:

This is a close-up from the first photo above, showing the apricot colour of the stipe as well as the tinges in the pileus, what I think is the very strong, prominent reticulation with somewhat elongated meshes, and the deep and very rapid blueing of the pores and flesh.

In the UK it is said to have a preference for calcareous soils and to associate with Beech particularly, Oak and Limes, sometimes conifers. In mountainous regions it has been found in the presence of Mountain Avens. 

It should have had a pleasant fruity odour, although I didn't check. It is very variable, with named red and yellow varieties, and seems well spread throughout the UK, although not quite so well represented in Scotland, Wales and Ireland.

I had another look the following day at the same stand, and was able to separate the pore layer from the flesh above to reveal the base of the cap flesh from below and the thin layer of red (Bataille's line) that is characteristic of this species. In this specimen, not the best perhaps, it looked pink, with blue where bruising had occurred, and showed the "indentations" of the pore layer very clearly. The pore layer came away quite cleanly on the third attempt and this was definitely fun, as well as excellent confirmation of the announced identity!

I also looked more carefully for a better shot of the red reticulation over yellow, and here is the result, which I think is a little more convincing, although still not with as clearly elongated meshes as I was expecting.

Brown Rollrim, Paxillus involutus s. l.

 

Paxillus involutus (Batsch) Fr. is a very common and also highly toxic mushroom indeed. It'll quite likely get you in the end, destroying your red blood corpuscles after your own immune system is eventually triggered to fatally turn on you.

It is related to the poroid fruiting bodies. The gills become more pore-like as they become decurrent down the stem, and it is said that they are detachable as a layer by pushing with a finger tip at the apex of the stem. 

I couldn't really detect much downiness in either cap, although this is noted in the literature to reduce as the caps age.

Note the brown staining when handled or otherwise bruised. There is indeed a slight umbo in the shallow central depression of the cap in this quite regular cap, possibly not too old a specimen. 

In the second photo, where the cap has been turned upside down, the fluting around the edge as reported in the literature is very clear.

And another larger, somewhat more distorted (a partial rose-comb aberration perhaps?), cap nearby. 

The fluting around the rim of the cap is far more limited in extent in this specimen.

Paxillus involutus s. l. (Batsch) Fr. is a species complex of at least four species, distinguishable by DNA analysis. These fruiting bodies might be the nominate species, as they were growing in more acidic soil and close to Birch, Paxillus involutus s.s.