Mushroom on a chestnut burr.

[bobby b]

Saw these tiny gilled mushrooms on an asian chestnut burr. A toadstool ready for battle.

[Dave W]

That's an interesting habitat. Maybe a species of Gymnopus? Looks like some sort of white-spored saprobic type. Coincidentally, I found the one pictured in this post yesterday. It's growing on a hollowed out acorn cap. I proposed genus Gymnopus on Mushroom Observer, and other users have shown support for genus Marasmiellus (which includes species formerly housed in Gymnopus). 

 

[bobby b]

Saw Marasmiellus candidus at cooks forest last spring. Not your acorn mushroom. Looks like the top photo shows another growing out of the moss.   I was looking for Gymnopus semihirtipes when I saw the little mushrooms on the chestnut burr. Haven't found G. semihirtipes this year.  

[Dave W]

Good eye, bobby! I had not noticed the tiny orange mushroom. It's a species of Galerina. 

[bobby b]

I put this on Inaturalist, 5/17, and Garrett Taylor said probably a Galerina. Crazy tall stature. Maybe G vittiformis.

[Dave W]

G. vittiformis looks like a good bet here. There are a number of different Galerina species that grow in moss. At least some of them tend to occur in May or early June, and maybe again in the fall. The very long stipe is the result of the mushroom needing to reach up high enough to be above the moss bed. Microscopic analysis is often necessary to pin these small/tiny Galerina mushrooms down to species.  As seen on Mushroom Expert, the species name "vittiformis" is thought to represent several different species. 

Here are two different/similar examples I collected last week (for study). https://mushroomobserver.org/411738?q=1FU1k     https://mushroomobserver.org/411740?q=1FU1k