Sac Fungi

A sac fungus and a slime mould

When hiking through the woods, I noticed this fungus growing on an old rotting stump. The way in which the fungus looks like the stump’s ear made me smile, and I stopped long enough to take a photograph. I touched the cup to get a sense of its texture. It was firm and rather rubbery.

My mycological expertise is limited to a few common species, but I recognised this cup-shaped growth as a sac fungus. None of the choices in my guide book, George Barron’s Mushrooms of Ontario and Eastern Canada, seems to match my find exactly, but it most closely resembles Humaria hemisphaerica. Correction: David William Fischer of AmericanMushrooms.com identifies this fungus as a Peziza species, likely P. praetervisa.

I was interested to read that sac fungi make up the largest division of all the fungi and are very diverse. Sac fungi are so named because the spores are produced in a sac-like cell, not because the fungi themselves are sack-shaped. The sac fungi include some very well-known members such as morels and truffles. Also included in this category is a species most gardeners recognise, powdery mildew (Erysiphe chichoracearum).

Under the cup fungus, you can also see clusters of small round orangy-brown dots. It’s a type of slime mold, probably a Hemitrichia spp. as per Mr. Fischer. Unfortunately, I didn’t notice it till I got home and looked at my photo of the cup fungus, or I would have tried to get a better photograph of the slime mould as well.

Powdery mildew on phlox leaves

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Fuligo septica

When I stepped out the front door one day last week, a flash of bright white on a log stump at the edge of the garden caught my eye. I used the log last summer to sit a potted plant on, and the stump has been waiting out the winter there. On closer examination, I found several white masses, a type of fungus, growing on the log. The growth was damp and when I gently poked it with a finger, I found it to have a soft, spongy texture.

I thought the fungus was probably a slime mold, but nothing in my field guide, Mushrooms of Ontario and Eastern Canada, by George Barron, seemed to resemble it exactly. The most likely candidate is Fuligo septica, of which Barron says this:

Fruitbody (aethalium) is a cake-like mass, up to 20 cm in the longest dimension by 3 cm thick, white, yellowish, ochre or red-brown, and with a smooth but brittle crust which breaks away to reveal a black spore-mass. Widespread and common, F. septica can migrate 1 m or more to fruit on stumps, logs, or living plants, often in the rich soil of well-manured gardens.

Although initially spongy, the mass did develop a shiny, brittle crust within a day or so, and over the next few days, the crust deteriorated and cracked to display a solid dark-coloured mass below. When I lifted the edge of the mass from the log, it disintegrated.

Although the photograph in Mushrooms of Ontario wasn’t convincing, the description does seem to match this fungus, as does it’s location on a log in a garden. Such discoveries always remind me of how much goes on right beneath our noses, mostly unnoticed. How complex the natural world is. How ignorant we are. I’m glad I discovered F. septica.

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