Saturday, October 31, 2015

Mushroom: Tetrapyrgos nigripes

August 21st. It had been raining. I had found small, white mushrooms on the ledge above the creek at our place and then found them throughout a section of the north-facing trail at Fort Yargo State Park. I took the time to find, and photograph, a particularly attractive cluster of mushrooms that were growing on a small twig. 

I suspected that they were members of the family Marasmiaceae that contains tiny mushrooms that are often easily overlooked in the woods. Marasmid mushrooms break down leaf litter in oak/hickory woods in eastern North America. Unlike most marasmid mushrooms, it would be very hard not to notice these mushrooms with their white caps, tiny as they are. 

I decided to try and work my way through the identification keys. I always find identification keys frustrating if I haven’t managed to collect all the information necessary to answer the questions. But this time I was in luck. 

#1 Decaying tree litter; they were growing on tree leaves and twigs.
#10 On debris of hardwoods; these mushrooms were growing on a hardwood twig.
#27 Growing on debris of other hardwoods (other than madrone, tanoak, sycamore, black locust, birch, quacking aspen, black cottonwood, or American holly); none of these trees grew in these woods.
#38 Odor not distinctive (somewhat foul, spermatic, bleachlike, mealy, or radishlike – but not of garlic); these mushrooms had no detectable odor.
#41 Fresh cap otherwise colored (not rose pink, red, purplish red, or wine colored); the caps were white.
#46 Mature cap rarely as wide as 2-3 cm; stem wiry or not; the caps were usually less than an inch in diameter.

#53 Fresh cap white or nearly; the caps were certainly white.

#54 Cap smooth to wrinkled or faintly linked but not conspicuously pleated; the caps were wrinkled.
#56 Not as above (caps larger than 2 mm maximum width; not growing on leaves of American beech); the caps were larger than 2 mm and were not growing on leaves or twigs of American beeches.

#57 Stem surface finely to prominently hairy; hairs were certainly visible on the stems of these mushrooms without having to use a magnifying glass.
#59 At least the bottom portion of the stem darkening to brown, dark brown, or black with maturity; the stems were dark brown/black at the base, progressing to white just below the cap.
I got to question ...
#61 Stem black except at the apex (at the cap); spores triangular to jack shaped: and there it was... Tetrapyrgos nigripes. 

Now I didn’t have spores, but the description of Tetrapyrgos nigripes fit these little mushrooms to a ‘T.’ Their caps were white and pleasantly wrinkled and usually less than 1 inch in diameter. Their stems were dark brown or black at the base and becoming progressively lighter up the stem until they were white near the cap. Hairs were visible on the stem. In addition, they exhibited a characteristic not mentioned in the keys - the stems of these mushrooms appear to be attached to the substrate stem or leaf without any apparent basal mycelium, the vegetative material of the fungus. In fact, it looked as if they grew directly out of the wood.

To add to these characteristics, these mushrooms form fascinating patterns when viewed from below. 

These mushrooms are distributed widely distributed east of the Mississippi River. In spite of apparently being relatively common, I hadn’t seen reports of them and it took me several years to identify them. In fact, I had misidentified them as a Marasmius sp. several years ago.

When I shared photographs of these mushrooms on Facebook, many people commented on having seen them in nearby woods. Too bad these little mushrooms have gone unacknowledged. 

Next time you see these in the woods, spare a few minutes to take a closer look at these little gems.


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