Forget leaf peeping, this is the height of mushroom season in New England and the various fungi that inhabit our woods and fields are more colorful than any autumn leaf. During a mushroom walk in my woods the other day I counted more than 20 different species of fungi along just one stream bank. However, while gazing at some particularly attractive Pholiota mushrooms on a decaying log, I noticed tiny gray spheres — wolf's milk slime mold — and got so excited that I forgot about the fungi.
Slime molds are colorful, fanciful creatures. Blackberry, toothpaste, many-goblet, chocolate tube and scrambled egg slime all have interesting stories to go along with their names. Wolf's milk slime, for example, is so named because when the nonmoving, reproductive structure is young it secretes a pinkish, milky substance (which gives it its other common name "toothpaste slime") that evidently reminded someone of wolf's milk — I have never milked a wolf so I can't confirm the resemblance.
Like fungi, slime molds are beautiful and strange and well worth learning about. One of my biology textbooks has a great section title, "Slime molds are fungus-like protists." That's quite a mouthful and an excellent example of how confusing it can be to lump some of the weird life forms of our world into easily understood groups. Something like a horse is easy — that's an animal, and a toadstool is a fungus, a palm tree is a plant. But what about a slime mold? It moves like an animal but produces fruiting bodies (reproductive structures) that look like mushrooms.
For years slime molds were housed in the Kingdom Fungi, but more recently, as a result of better understanding of their biology they have been moved into the Kingdom Protista, the taxonomical equivalent of the island of misfit toys, the kingdom into which most life that defies easy categorization is placed.
The particular slime mold that first piqued my curiosity about this group was the wolf's milk slime mold. When I first saw one I thought it was a mushroom, it resembles a tiny puffball mushroom, and, when prodded, will release a delightful cloud of spores (just like a puffball). This spherical form of the wolf's milk slime mold (scientific name, Lycogala epidendrum) is the last stage in a wonderfully confusing life cycle.
Wolf's milk slime mold is a plasmodial slime mold, a group of slime molds that spend part of their lives as a large single cell (from tiny to over 12 inches) containing many nuclei called a plasmodium. The plasmodium spends its time moving through the soil, under logs and over dead leaves and grass munching on bacteria. If this mass absorbs a bacteria it doesn't like, it will spit it out.
The dog vomit slime (which looks just like its name) is a commonly seen representative of this stage. Then, some environmental trigger, such as a decrease in the food supply or low moisture, will trigger a change; the plasmodium will stop moving and form reproductive structures that produce spores. These structures often resemble mushrooms. The reproductive structures dry out and release spores. When conditions are right, the spores begin to creep about like amoeba, or develop flagella and swim. Eventually the spores will move together and fuse to form a new plasmodium.
If you are interested in learning more, you will find descriptions in most guides to common mushrooms (even though slime molds aren't fungi). Lawrence Millman's "Fascinating Fungi of New England" or George Barron's "Mushrooms of Northeast North America" are great places to start.
Sue Pike of York has worked as a researcher and a teacher in biology, marine biology and environmental science for years. She teaches at St. Thomas Aquinas High School. She may be reached at
