Excerpts from Jim Conrad's
Naturalist Newsletter

Entry from field notes dated September 1, 2023, taken in Los Mármoles National Park in the Eastern Sierra Madre mountains, Hidalgo state, MÉXICO, along steeply climbing road heading eastward out of town of Trancas {on maps designated "Morelos (Trancas)"} toward Nicolás Flores; juniper/pine forest on limestone bedrock; elevation ~2,300m (~7,550ft); ~N20.80°, ~W99.25°
HEMIONITIS EMPERATRICELLA also known as Pellaea sagittata

HEMIONITIS EMPERATRICELLA [Pellaea sagittata], in habitat on stone wall

The above fern was rooted in mossy spaces between rocks in an old stone wall with fill dirt on the other side -- an effort to keep the slope from sliding onto the road. During a long-term and ongoing severe drought, new leaves mingled with dried-up stems of previous seasons.

HEMIONITIS EMPERATRICELLA [Pellaea sagittata], a single 2-pinnate leaf or frond

A single leaf, or frond, is shown below. It is twice pinnate, meaning that the blade is divided into primary divisions, or pinnae, which themselves are divided into subdivisions, or pinnules. Note pinnules at the blade's tip, at the image's top, right corner, are triangular, while lower down, over my hand, they're roundish and somewhat heart-shaped.

HEMIONITIS EMPERATRICELLA [Pellaea sagittata], close-up of pinnules' lower surface showing immature false indusia

For identification purposes, the revealing feature shone above is that the pinnules' margins are curled under all the way around; we're looking at the pinnules' undersurfaces. Such curved-down margins are a distinguishing feature of the big fern family known as the Pteridaceae, and are referred to as "false indusia." These are freshly emerged pinnules on which granular, spore-bearing sporangia have not yet appeared crowding beneath the turned-under margins. Also for identification purposes, it's important to notice above that the stems -- the larger rachilla and the stalk of each pinnule, the petiolules -- are pale, not black, and pinnule bases produce backward-directed lobes.

At first glance, the fern's small pinnules dispersed as parts of a large multiply compound blade might suggest one of many commonly encountered maidenhair species. However, closer up, the underturned pinnule margins are not separated into little lobes, so that's more like the cliffbrakes, such as Pellaea truncata.

In fact, most literature accessible at this time, based on features noted above, would direct us to the cliffbrake genus Pellaea. Mainly because the pinnules shown in the above picture are somewhat triangular, with backwardly projecting lobes -- they're sagitate -- various floras identify our fern as Pellaea sagittata, with no English name other than the general "cliffbrake."

However, Kew's Plants of the World database and the International Plant Names Index, both frequently updated, assure us that the name Pellaea sagittata now is to be considered a synonym of HEMIONITIS EMPERATRICELLA. Apparently this is a name change based on new studies.

Traditionally, species of the genus Pellaea have been known as cliffbrakes, while species of Hemionitis (which most of my life I've known as Cheilanthes) were known as lipferns. Now it's unclear whether our fern eventually will be known as a cliffbrake, lipfern, or something else. That's how it goes these days: More insights from detailed studies often brings more confusion.

Whatever the best name, our fern is described as inhabiting exposed rocky places, shady narrow valleys, oak and oak-pine forests, and subtropical scrub throughout Mexico's uplands, south into Guatemala, and then the species appears again in western South America, south to Argentina. It's not particularly common, but turns up spottily over a large area.

I read that in Argentina it's been used in traditional medicine, though there's no mention of how and for what ailment.