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Excerpts from Jim Conrad's
Naturalist Newsletter

from the November 13, 2006 Newsletter issued from Diego Nuñez's office above Restaurante "Isla Contoy," Río Lagartos, Yucatán, MÉXICO
GIANT LEATHER FERNS

South of town, waterlogged mangrove doesn't always give way just to thin-soiled, cactus-rich, desert scrub. In some places mangrove yields to grassy marshes -- clumps of grass rooted in mud, with soil between clumps either submerged beneath saltwater or soaked. Often, even in this important, officially recognized "Biosphere Reserve," cattle graze these marshes.

Sometimes Giant Leather Ferns, ACROSTICHUM DANAEFOLIUM, emerge from the soggy grassland. Taking in their effect, one might say "emerge like a Viking on a beach." In fern terms, these are huge, coarse-looking things giving the impression of having been rooted exactly where they are since dinosaur times. That's one of them below, with fronds soaring nearly nine feet (2.5 m) above the muck.

Giant Leather Fern, Acrostichum danaefolium

In the above picture the inset on the right shows a close-up of the fern's fertile pinnae. There you can see that this species produces its dusty, cinnamon-colored spores not in dainty clusters of spore-producing sporangia, like the North's little Woodsias and Shield Ferns, but rather they are randomly and abundantly spread across the entire lower surfaces of fertile pinnae.

Actually there are two species of Acrostichum fern found in places like ours, and I bet the other one, A. aureum, called Mangrove Fern, Golden Leather Fern, Swamp Fern and a host of other names, is found here, too. The "Flora of Quintana Roo" lists both species.

Speaking of that "Flora of Quintana Roo," which was written in Spanish and gives plant names in Latin, sometimes when you know what a plant's family or genus is it's helpful to have a list of species known to occur in the families and genera of the area you're studying, or next to. For example, I knew from experience that I had a Pedilanthus in the Mammillaria habitat shown above, but I had no idea which Pedilanthus it was. The "Flora of Quintana Roo" listed only Pedilanthus tithymaloides for that contiguous state, it looks like that species when I Google it, so a good guess is that what's shown in my picture is that species.

The "Flora of Quintana Roo" can be downloaded at http://biblio68.ibiologia.unam.mx/FullText/lfl2.html.


from the October 16, 2011 Newsletter issued from Mayan Beach Garden Inn 20 kms north of Mahahual, Quintana Roo, México
LEATHER FERNS IN THE MANGROVES

At high elevations we've run into tree ferns, so we're familiar with big ferns. However, the big fern found at the edge of a mangrove swamp the other day was notable for its large size because it wasn't a tree fern. It was just a really big fern growing on the ground the regular way. You can see part of a frond below:

Giant Leather Fern, Acrostichum danaefolium, pinnae

The fern grew in dense brush so I couldn't step back for a picture of the whole eight-ft-tall plant. Some frond sections, or pinnae, were producing heavy crops of brown spores on their lower surfaces, as shown below:

Giant Leather Fern, Acrostichum danaefolium, fertile pinnae

This is a Leather Fern, genus Acrostichum, a genus distinguished by the large size of its species, by the species' swampy, marshy habitat preferences, and by the way abundant spores are produced across the whole lower surface of pinnae instead of in neat little "fruit dots" like those we've seen on most ferns we've encountered.

Two species of Leather Fern are found in our area: Acrostichum aureum and A. danaeifolium, and they're fairly similar. Spore-bearing pinnae of A. aureum are limited to the fronds' topmost pinnae, while on A. danaeifolium spore-bearing pinnae occur throughout most of the frond. The latter seemed to be the case with our plant, so I'm thinking that our photo shows Acrostichum danaeifolium. More distinctions are given on the Flora of North America Acrostichum page here.  

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