Hello,

the pigment in H. fuscoides have been observed to change in time. A collection of H. fuscoides with purple pigments was checked again 1,5 year later and gave just dull gray (slightly purplish) pigments. See here: http://www.czechmycology.org/_cmo/CM69106.pdf 
(I'm not saying anything about this collection, not enough experience with Xylariales.)

Viktorie 

Hi Viktorie
Very interesting study and especially the comments included in the description! According to them, most of the features of my collection go well with H. fuscoides (substrate, small sporocarps, spore dimensions).
However, even a little bit of purple is missing during the KOH test. Yesterday I carried out the test on about 10% KOH so today I repeated it with diluted (about 3%). However, the effect remained the same.
Therefore, it is difficult to decide which criterion is more important: the size of the spores or the color of the KOH extract?
However, because the color of the extract does not completely correspond to H. fuscoides, so my collection cannot be considered as this species. Even though the color changes with age, this purple shade remains minimal.
Therefore, since other features are compatible with H. fuscum and spores despite their small size, however, are within the lower limit for H. fuscum, it is safer to consider my collection as H. cf. fuscum?
Thank you and best regards
Mirek

I must include a small correction to my previous statement.
Immediately after placing the fruiting sample in KOH, a reaction similar to the 10% solution occurred.
However, before I wrote the previous post and checked the reaction again (about 20 minutes later), it turned out that its color changed a lot.
Can the concentration of KOH have such a big impact on the color ???
Today, I used a sample of the same fruiting body as before.
In this sample I see a shade of purple.
What is your opinion on this subject?
Mirek

This is in that 3-5% KOH? Both pieces from the same stroma? 

Personally, I'm using 3% KOH in both Xylariales and Otidea, works ok. I heard from someone that in very high concentrations (like 30 %) the colors are less distinct, lighter, perhaps because the pigment is both extracted and altered/damaged. But really, Jacques (and others) is the specialist here. ;-) 

Thanks for explanation.
I never used KOH too much, so I didn't pay too much attention to its concentration.
I wonder, however, why it was at low concentration that a variable response occurred and not at high? Perhaps it was the purple pigment in high concentration that was destroyed?
Although it is not a pure purple shade, it is only quite strong darkening the preparation.
I will make a few more samples at different KOH concentrations and see how it looks.
Thank you
Mirek

I made several samples at different KOH concentrations.
On the left is a sample placed in about 10% KOH solution. The further to the right the lower the concentration. Unfortunately I did not measure.
It turns out that the concentration has an effect on the color obtained. Also the time after which we watch the sample.