I guess that you could say that I am on a roll.

If you read last week’s column, you may get the pun. For those that missed it, the article was a thanks giving to yeast and the bread and booze that it provides. While it wasn’t my intention to continue the thread (another pun that will soon be clear), I find that, after a CSI-style investigation, I am back on the fungus track.

The mystery that has brought me to mulling mushrooms begins in Technicolor — bright blue-green, to be exact. For years I have noticed pieces of rotting wood on trails that have surprised me with their brilliant blue-green color. Having asked around, I received vague answers from fellow naturalists.

Was it animal, vegetable or mineral? None of the above, to be clear. What it is, is the result of a fungal infection. Perhaps there is a dark side to the fungi of which I spoke so highly last week.

Green elf cup fungus, Chlorociboria aeruginascens (aerunginascens actually means ‘blue-green’) is the likely culprit, although another species of Chlorobiboria does exist in North America and might also be to blame. Chances are that you will never see the actual little mushroom that causes the richly colored wood. Most of my sources note that it is rare to see the fruiting body of the mushroom as it only occurs after very prolonged wet periods. Chlorociboria looks like a small bright green cup.

The main clue to the presence of this fungus is the colored wood — called green wood, green stain or green rot — that it leaves behind. The blue- green staining occurs mainly in oaks, and green oak is highly prized due to its incandescent emerald hue. Italian Renaissance woodworkers used it during the 14th and 15th centuries in their inlaid intarsia designs. In Britain during the 18th century, it was an integral part of Tunbridgeware, small boxes inlaid with animals, flowers or other designs that were made in Tunbridge, Kent, England.

Oaks are not the only victims of this fungus. Beech and hazelnut wood is also susceptible. The color staining is caused by a pigment called xylindein that is found in the mycelium or threads of the fungus. This chemical pigment can inhibit plant germination and is being researched as a possible algaecide, a pesticide that makes wood less appealing to termites, and for its potential to fight cancer. Green goodness!

Green cup fungus is a non-edible mushroom. It is a saprobe, or soft rot fungus, which means that it survives by decomposing already dead and rotting organic matter. Thus it is not found on living trees and won’t kill healthy wood.

So while not deadly, this elusive elf leaves its mark behind. It is not black magic, but blue-green enchantment that brightens up the otherwise dreary winter forest floor.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.