Argyrochosma lumholtzii facts for kids

The Argyrochosma lumholtzii is a special kind of fern that is quite rare. It belongs to the Pteridaceae family and is mostly found in Sonora, Mexico. This fern is sometimes called Lumholtz's false cloak fern.

It looks a lot like another fern called Jones' false cloak fern. However, you can tell them apart because Argyrochosma lumholtzii has black stems on its leaves. Its leaves are also not as divided as the other fern's. Scientists first described this fern in 1939. They named it after an explorer named Carl Sofus Lumholtz. Later, in 1987, it was moved into a new group of ferns called Argyrochosma, which are known as "false cloak ferns."

What Does This Fern Look Like?

Argyrochosma lumholtzii is a small fern. It has a short, upright rhizome (which is like an underground stem). This rhizome has thin, straplike scales that are about 4 to 5 millimeters long. These scales are orange-brown or reddish-brown and have smooth edges.

The leaves of the fern grow in groups from the rhizome. Each leaf, from its base to its tip, is about 7 to 15 centimeters long. Most of this length is the stipe, which is the shiny, round, black stalk of the leaf.

Leaf Shape and Texture

The main part of the leaf, called the blade, looks like a triangle or an egg shape. It is divided into smaller sections. The central stem of the leaf, called the rachis, is round and black, just like the stipe.

Each leaf usually has 6 to 8 pairs of smaller leaf sections, called pinnae. These pinnae are spaced out and grow alternately along the main stem. The pinnae are further divided into even smaller, round or slightly oblong sections called pinnules. These pinnules are about 3 to 4 millimeters wide and have smooth edges. The very tip of the leaf is also triangular.

The leaves are a gray-green color and feel a bit leathery. Unlike many other ferns in its group, the underside of this fern's leaves does not have a powdery coating.

Spores and Reproduction

The fern's spore cases (called sori) are found along the veins on the underside of the leaves, close to the edges. The edges of the leaves might curve slightly, but they don't form a special cover for the spores. Each spore case holds 64 spores. This means the fern reproduces sexually, using these spores.

This fern is most similar to Argyrochosma jonesii. However, you can tell them apart because A. lumholtzii has black leaf stems, while A. jonesii has brownish ones. Also, the leaves of A. lumholtzii are divided fewer times than those of A. jonesii.

How Scientists Named and Classified This Fern

Scientists William Ralph Maxon and Charles Alfred Weatherby first described this fern in 1939. They named it Notholaena lumholtzii to honor Carl Sofus Lumholtz, who collected the first samples of this fern in Sonora, Mexico. They thought it was closely related to another fern called Notholaena nivea.

In the 1940s, other scientists, like Edwin Copeland, suggested that this group of ferns might be different enough to be their own genus (a larger group of related species). This idea was finally put into action in 1987 by Michael D. Windham. He was studying how these ferns are related to each other. He created the new genus Argyrochosma for these "false cloak ferns" and moved Notholaena lumholtzii into it, renaming it A. lumholtzii.

More recently, in 2018, Maarten J. M. Christenhusz suggested moving this fern again, this time to the genus Hemionitis, calling it H. lumholtzii. This was part of a bigger plan to group many similar ferns together.

Scientists have also used genetic studies to understand how ferns are related. These studies show that A. lumholtzii is a "sister species" to A. jonesii. This means they are very closely related. These two ferns, along with A. formosa and A. microphylla, form a special group. All four of these ferns do not have the powdery coating on their leaves. Scientists believe their common ancestor split off from the rest of the Argyrochosma group before that powdery coating developed in other species.

Where Does This Fern Live?

Argyrochosma lumholtzii is very rare. It has only been found in a few places in Sonora, Mexico. The exact places where the first ferns were collected during the Lumholtz expedition were not written down.