Plasmodial slime molds are single-celled organisms, masses of protoplasm without cell walls and with thousands of nuclei. Like animals, they move and violently eject unwanted inorganic materials. Like amoeba, they feed by engulfing particles of food. Like fungi, they reproduce by producing fruit bodies containing spores that are distributed by wind. Formerly classified as fungi, plasmodial slime molds are now known to be unrelated.
Dog vomit slime mold (Fuligo septica) is a plasmodial slime mold. It has a worldwide distribution, occurring on every continent except Greenland and Antarctica. It is often found in urban areas from May to October. It grows on the rotten wood of stumps, logs, and wood mulches; on garden soil enriched with manure; and also on living plants. It may migrate one meter or more to nearby food sources. It feeds on bacteria, spores of fungi and non-flowering plants, protozoa, and nonliving organic matter. Its common name accurately describes its appearance. It is not edible.
Dog vomit slime mold may appear as a cushion-like mass, a slimy sheet, or a crust-like sheet. When it first appears it is white to yellow and slimy. At some point it transforms into a large, cushion-like, white or yellowish fruiting body covered by a brittle crust. Breaking the crust away reveals a dull black spore mass.
Protostelid slime molds are relatively unknown and easily overlooked. They were first recognized in the early 1960s and have been little studied since. There are 36 currently accepted species, and possibly twice that number of undescribed species. Most are microscopic. Only a few are visible to the naked eye.
Honeycomb coral slime mold (Ceratiomyxa fruticulosa) is the most commonly encountered protostelid slime mold and may be the most common slime mold of any kind in the world. It occurs on every continent except Greenland and Antarctica. It is found in forests on rotting fallen logs and branches. It can form extensive colonies one meter or more long. It is very short lived, appearing after a soaking rain and disintegrating in just a few days.
Honeycomb coral slime mold first appears as a thin, watery, translucent, mucus-like layer, creeping across the wood, engulfing bacteria, protozoa, and particles of nonliving organic matter. Eventually it fruits, forming clusters of erect, translucent columns. The columns have a frosted or powdery appearance due to a dense covering of tiny, white, spores on long, thread-like stalks.
Wasp nest slime mold (Metatrichia vesparium) is common and widespread. It is found in Europe, Asia, Africa, Australia, and North and South America. In the United States it is common east of the Great Plains, including Minnesota, less common in the west. It grows in open forests on dead and rotting wood, especially hardwood.
The fruiting body may be attached directly to the substrate or rise in a densely crowded group of up to twelve on a common stalk. The individual spore-producing structures are dark red or reddish-purple to nearly black, less than ⅛″ in height, and about 1 ⁄32″ in diameter. They are mostly cone-shaped and have a convex, shiny, iridescent, lid on top. When mature, the lid swings open like a jack-in-the-box, and the red or rust-red interior expands outward. When this dries out, the spores are disbursed by wind. Eventually, the expanded portion disintegrates. What is left looks like the nest of a paper wasp, giving this slime mold its common name.
Slime mold is a term of convenience grouping together several kinds of unrelated organisms. They were formerly placed in the Fungi kingdom because they produce structures containing spores (sporangia). The modern classification has them divided among several supergroups. The taxonomy of slime molds changes frequently—it is a work in progress.
Red raspberry slime mold (Tubifera ferruginosa) is one of the most commonly encountered slime molds in woodlands. It appears from June through November as a pink to bright red, pillow-shaped, tightly-packed mass on well-rotted logs, sometimes on moss. The surface is knobby, like a raspberry. It is not edible.