The forest floor around here is very dry just now, in spite of the heavy rain we have had in the days before the brief heat wave. Nevertheless, I am beginning to see the occasional mushroom popping up again, like this deer shield growing from a crevice on a birch tree.

While seemingly common in the UK, this is a new-to-me mushroom that I have not stumbled upon in this area before. I could see straight away, thanks to the cracked cap, that it was some kind of a pink gill, and of these the deer shield was the most likely candidate; this is confirmed by microscopic analysis.

The cap is brown, radially streaked, 4cm in diameter, stem is streaked grey, 0.5cm in diameter, flesh is white.

mushroom from below, showing gills

The gills are slightly pinkish in tone, crowded, free from the stem, with quite a few of them being short.

mushroom from below, showing gills

cross section of a mushroom showing gills detached from stem

Spore print is pink, with the spores irregularly oval, in this specimens averaging 6.58 x 4.95 µm and Q of 1.34, as seen the following image (mounted in KOH):

mushroom spores under a microscope

The pleurocystidia (sterile cells on the surface of the gills) are decorated by ‘antlers’ — this is the key identifying feature for this mushroom, that separates it from the visually similar Pluteus podospileus.

mushroom gill under a microscope, showing cells on the gill surface

In some sources the decorations are said to be on cheilocystidia (sterile cells on the edge of the gills). I do believe this is incorrect, my observation matches the microscopic description by Michael Kuo (FWIW, I find Kuo to the best online resource for microscopic and related description, even though his site is restricted to North American fungi).

The cheilocystidia are, in fact, bulbous and densely packed along the entire gill edge:

mushroom gill under a microscope showing the gill edge