Bitter Bolete

I've spent a fair amount of time trying to identify this Tylopilus bolete to species.  It was fairly easy to get to the right genus; Tylopilus boletes have pinkish pores (boletes have spongy pores under their caps instead of gills), but getting it to the species level was another matter, the descriptions of a number of Tylopilus species matched the mushrooms I had collected.  To keep everything straight I made a chart.

Since these were older specimens, some of the color characteristics of the cap, pores, and stem weren't quite as useful.  I narrowed it down to two species, T. felleus and T. rubrobrunneus.  This was based on the large cap size (almost 20 cm in diameter), and the bitter taste.  Two other features helped narrow it down.

First, many boletes "bruise", turning different colors when handled or cut.  The pores of the mushrooms I collected slowly bruised from pinkish to a darker brownish pink (I guess).  The white flesh of the cap and stem didn't bruise or very, very slowly discolored.

Second, some boletes show reticulation along their stems, or a kind of net-like pattern.  T. felleus shows strong reticulation, while T. rubrobrunneus shows none or weak reticulation on the upper part of the stem.  I think the mushrooms I collected had only slight reticulation on the upper part of the stem (see picture above), leading me to identify these mushrooms as T. rubrobrunneus.

One other test I did was to apply KOH and ammonium to the surface and flesh of the cap.  I got a slight yellow stain on the surface of the cap, but no reaction on the flesh which more or less matches the reactions seen in T. rubrobrunneus.

I was really excited when I found these mushrooms, they were so big and the bugs hadn't gotten to them yet (which is  usually the state I find big boletes in) so I thought they might make a good meal.  But they are quite bitter in taste.  But I found the mental challenge of sorting through their identification to be a satisfying experience (and I found plenty of chanterelles to satisfy to palate).

Tylopilus rubrobrunnens

A final note, the name "Bitter Bolete" is the common name sometimes given to T. felleus.  I haven't come across any common names used for T. rubrobrunneus.  If you translated the scientific name it would roughly mean Red-brown Bolete, which isn't bad, but Bitter Bolete works and makes for a nice title.