The common powderhorn is easy to identify. Like most other members of its genus, its main vegetative body consists of a carpet of gray-green, scalelike squamules, but its fruiting bodies (podetia) are unique: elongated conical prongs, looking like small upright horns or worms. These tiny, grayish, often bent stalks grow out of the center of a squamule and are coated with powderlike soredia (tiny fragments of the lichen that can break away and form a new lichen elsewhere). The hornlike podetia in this species are sterile: they do not produce spores, for they almost never develop cuplike or ball-shaped apothecia.
The common powderhorn is considered a fruticose lichen, meaning it is three-dimensional as opposed to flat or crusty. Like other lichens in its genus (called cladoniform lichens), the thallus (main body) is a patch of grayish-green squamules. Cladoniform lichens have a variety of reproductive structures, including clubs with colored tips, tiny goblets, or shrubby branching structures.
A lichen is an organism that results when a fungus species and an algae species join together. Although the relationship between the fungi and algae is quite intimate and integrated, the lichen that is formed does not much resemble either of the components. Learn more about lichens on their group page.
Similar species: Missouri has about 37 species in genus Cladonia, most of which, at some point in their life cycle, exist as patches of rather unspectacular greenish or grayish, scalelike squamules. The various shapes, colors, and textures of the fruiting bodies are important for identification in this group. The common powderhorn is fairly unique with its horn-shaped podetia.
- One Missouri relative, stalkless cladonia (Cladonia apodocarpa), like other cladonias, has its main body resembling a little carpet of tiny, flattened, blue-gray, curling, lobed leaves growing as a small mat on the ground. In that species, however, podetia and apothecia are rare. The stalkless cladonia is common on soils in dry woods but is easily overlooked: It’s easy to assume it’s one of the other clads that simply hasn’t yet formed podetia.
Podetia height: usually less than 1 inch. This species and other cladoniform lichens, as they spread, may cover several square inches of substrate.
Statewide.
Habitat and Conservation
The common powderhorn usually grows on old, damp, rotting wood, often on tree bases, often in shady, moist areas such as damp, wooded slopes. Rarely, it grows on bare soil.
Cladonia lichens are some of the first to disappear when a natural habitat is disrupted, and they are sensitive to pollution.
Life Cycle
Lichens usually can reproduce vegetatively or sexually. In the case of common powderhorn, however, sexual reproduction is rare, since it almost never forms apothecia (spore-producing structures) on its hornlike podetia.
Vegetative (asexual) reproduction occurs when a piece of a lichen’s thallus breaks away and begins growing independently elsewhere. The thallus of cladonia species (the patch of green scale-like squamules) may easily be damaged and portions of it moved elsewhere.
Another way this lichen can reproduce asexually is via the soredia that form on the horns, making them look dusty or powdery. Soredia are special, tiny structures that amount to little packets of the lichen, containing sample of both fungal and algal components. The soredia break away easily and can form new lichens that are genetic clones of the parent.
Human Connections
The common powderhorn and its relatives are a joy to any photographer with a closeup lens.
Lichens are common yet mysterious. Use a hand lens to examine these combo-organisms. You may see insects living among them. The seemingly primitive nature of lichens, mushrooms, and mosses and other nonvascular plants makes them wondrous.
Lichenology is the study of lichens, and now is a great time to learn about them. Online references abound, with plenty of great closeup images. Consulting a specialist is just an email away. Not long ago, limited to in-person field trips with professors and the constraints of publishers’ printing budgets, budding lichenologists had to use black-and-white drawings in thick reference volumes in college libraries.
Ecosystem Connections
The common powderhorn and other cladoniform lichens, as they grow across damp, decaying logs, often live among mosses such as juniper haircap moss, fern mosses, broom mosses, tree apron mosses, and others. These create a microhabitat for small animals such as earthworms, centipedes, sowbugs, springtails, snails, a wide variety of insects, and more. Shrews, salamanders, frogs, tiny snakes, and other animals hunt for the various small animals in these habitats.
Mosses, liverworts, hornworts, and lichens seem rather similar, but these organisms are in very different groups. Mosses, liverworts, and hornworts are small, low plants usually found in damp habitats. Unlike more familiar plants, they lack veinlike structures and do not produce flowers or seeds — instead, they produce spores. Meanwhile, lichens are not plants at all: they are a collection of different fungi that have photosynthetic algae living within their tissues.