January 11, 2015
It all happened too quickly. On a trail deep inside the mangroves we passed beneath an Amate, a strangler fig tree, beneath which many green, immature, fruits littered the forest floor. Why were those immature fruits on the ground and not ripening on the tree? Diego looked around, trying to understand, and saw the reason: They'd been dropped there by spider monkeys, and at that very moment the monkeys were swinging through the treetops escaping. Following Diego, I reeled around and snapped the poorly framed picture at http://www.backyardnature.net/n/15/150111mk.jpg
When a human sees wild monkeys being themselves, there's a certain flash of recognition of common roots: The monkey turning its head for one last look at you before disappearing into seclusion; the wrists and knees angling in a certain familiar way; the curve of a flexible spine just right for multitasking; the all-too-familiar pot belly. Other animals with their rigid exoskeletons and with eyes on the sides of their heads and elsewhere can't arouse such empathy as I felt at that moment.
Back in the 70s and 80s I used to see spider monkeys regularly in the vast lowland forests of Chiapas and northern Guatemala, but now those forests are mostly gone, converted into weedy cornfields and ranchland. Once northern Yucatan's forests also hosted Howler Monkeys, whose roars send a chill through you on foggy mornings, but now that species is extirpated even here. Seeing these Spider Monkeys that somehow have held on here was very good.
Spider Monkeys, sometimes more formally named Geoffroy's Spider Monkeys or Black-handed Spider Monkeys, are ATELES GEOFFROYI, and they occur from southern Mexico south through Central America and possibly into a small part of Colombia. Some primatologists regard the Black-headed Spider Monkey of Panama, Colombia and Ecuador as the same species and if that's so then the species extends a bit more into northern South America. Usually seven subspecies of Geoffroy's Spider Monkey are recognized. Ours is Ateles geoffroyi ssp. yucatanensis, present in the Yucatan Peninsula, northeastern Guatemala, and adjoining parts of Belize.
Though when swinging through the trees spider monkeys seem light and agile, they're one of the largest of all New World monkeys, weighing up to 20lbs (9kgs). Still, their long tails are strong enough to support their entire weight when they dangle from a limb. In our picture you can see that their arms are longer than their legs. Their hands bear only a vestigial thumb, but their strong fingers are long and hook-like.
Geoffroy's Spider Monkeys are known to spend 70 to 80% of their feeding time eating ripe, fleshy fruit, such as figs. I'm guessing that the unripe figs beneath the strangler had been picked, tested, and found to be too hard to eat. The species also eats young leaves, which provide protein lacking in many fruits, and flowers, bark, insects, honey, seeds and buds. Water needs are largely met by the juice in the fruits they eat, but also they drink from tree holes and from what collects at the base of certain bromeliads up in the trees. Sometimes they descend to the ground to drink
The IUCN Red List of Threatened Species regards Geoffroy's Spider Monkey as an endangered species, stating that "... habitat loss across its range has been severe such that it is estimated that the species has declined by as much as 50% over the course of the past 45 years (three generations)."
Think of the impact on human society if grandparents had to tell their grandkinds that during their lifetime half of all people on Earth had disappeared.
Recent studies using mitochondrial DNA indicate that spider monkeys branched off from woolly monkeys and muiriquis about 3.6 million years ago. On the Phylogenetic Tree of Life, New World monkeys as a whole diverged from the branch on which Old World chimpanzees, humans, gorillas, orangutans, gibbons and Old World monkeys continued to evolve and diverge about 32 million years ago. Humans separated from chimpanzees only about five to seven million years ago.
Our spider monkey picture isn't the only hastily snapped and poorly focused image of a very interesting mammal taken this week. Tuesday morning, in the extreme northeastern corner of Yucatán State, we were hiking the little-used dirt road into El Zapotal, an isolated protected area administered by the important Mexican environmental group Pronatura, when Diego was first to spot, maybe a hundred yards (meters) up the road, what's shown at http://www.backyardnature.net/n/15/150111tx.jpg.
"¡Tayra!" Diego let us know, though neither he nor I had ever seen a Tayra in other than books. With its black body and white head and neck it couldn't have been much else. Quickly the animals sensed our presence and scampered off the road, giving us a side view of their very low-strung bodies and long, thick tails, as shown in my even blurrier shot at http://www.backyardnature.net/n/15/150111ty.jpg.
Tayras, EIRA BARBARA, can be found in Mexico's southern half, except in the highlands, and all the way south to northern Argentina. Being distributed over such a large area, they're known locally by many names, but in the Yucatan the Spanish name Viejo de Monte normally is used, more or less meaning "Old Man of the Woods."
Tayras are omnivores, but they hunt, too, and can kill animals larger than themselves. In northern Argentina they've been seen chasing a brocket deer for hours, and when they caught it they began eating it while the animal still was alive. They climb trees and catch monkeys, squirrels and lizards, as well as smaller prey such as insects.
As you might guess from their short legs and long bodies, Tayra are members of the Weasel Family, the Mustelidae, in which also are found otters, badgers, martens, ferrets, minks and wolverines. Over their large distribution area, nine subspecies have been recognized. Our Yucatan ones are Eira barbara ssp. senex, occurring from Mexico to northern Honduras.
CATTLE EGRETS & LOCUSTS
Several times over the years we've documented enormous movements of locusts in the Yucatan. You can see amazing pictures and read about them at http://www.backyardnature.net/yucatan/locusts.htm.
In extreme northeastern Yucatán State this week our truck passed through a small flight of them as late afternoon sunlight caught in their silvery wings, surrounding us with fluttering, drifting globes of radiance. There must have been more of them out in the savanna beside the road, for that's where a flock of Cattle Egrets was busily gobbling up what could be caught, the flock keeping up with the locusts' general southerly movement. You can see some of the egrets at work at http://www.backyardnature.net/n/15/150111lo.jpg.
Cattle Egrets are well known for this kind of behavior. Often they follow farmers' plows collecting earthworms. Though they favor insects, especially grasshoppers and other small arthropods, they also catch frogs, fish, lizards, small birds and rodents. In areas where people set grassland ablaze thinking it improves grass production, as here, Cattle Egrets follow along beside the fire, preying on small creatures trying to escape the flames.
Salt-producing ponds at Las Coloradas just east of Río Lagartos occupy about 6900 acres (2800has). The ponds are separated from one another by narrow levees sometimes topped with one-lane dirt roads. It's good birding out there and with all that glaring sunlight, wind and blowing foam it's a dramatic landscape, but getting disoriented on those levee-top roads is a problem. The levees have been built with backhoes, using fill material from adjoining pond bottoms. The fill material mostly is loose and unconsolidated but inside it are many fair-size, white coagulations of cemented-together sand, mud and mollusk shells, such as what's shown at http://www.backyardnature.net/n/15/150111tl.jpg.
Though with a pen knife or even a fingernail usually you can drill a hole in these coagulations, they're hard enough to be called rocks. A few more millennia of compression by sedimentation above them, and continued chemical bonding of the kind that hardens concrete, might produce rock that without hesitation could be called limestone. This is limestone in its earliest state of formation.
Even the sand and mud forming this rock's matrix consist mostly of tiny seashells and seashell fragments. Normally seashells embedded in rocks are called fossils, so the question arises as to whether the seashells in these coagulations-becoming-rocks also are fossils. The term fossil is defined as "A remnant or trace of an organism of a past geologic age embedded and preserved in the earth's crust." Do the organism traces -- the shells -- in these incipient rocks come from a past geologic age?
The subdivision of geologic time beginning about 11,700 years ago at the end of the last Ice Age, or the Pleistocene Epoch, and lasting until now, is referred to as the Holocene Epoch, and the literature is full of references to Holocene fossils. Therefore, I'm calling mollusk shells teased from these very young rocks fossils, and I'm curious as to whether any fossil in them has members of the same species living in the ocean lying just across a narrow band of sand dunes from the salt ponds.
One such fossil pried from a rock with a stick and my fingernails is shown at http://www.backyardnature.net/n/15/150111tm.jpg.
That's a top view. You can see the same shell from behind at http://www.backyardnature.net/n/15/150111tn.jpg.
The fossil consists of two shells, each shell the mirror image of the other, and you can visualize that when the mollusk was alive the two shells could be opened by hinging at the point on the back where the two tooth-like projections meet. A side view is shown at http://www.backyardnature.net/n/15/150111to.jpg.
Though time seems to have bleached color from the shell, we can still see fine details enabling this shell to be identified. Specifically, near the bottom of the shell, notice that the warty projections are sharply pointed on top, but become blunt both behind and in front. At the front of the shell, the warts become scoop-shaped, with the scoop openings facing forward.
These are features of the Yellow Prickly Cockle, DALLOCARDIA MURICATA, in older literature referred to as Trachycardium muricatum. Yellow Prickly Cockles are commonly found living today from North Carolina on the US Atlantic coast, south through the Gulf of Mexico and Carribbean and all the way to Brazil. Confidence in the name is increased by the species being one of several identified by experts found during archaeological excavations of the Southern Plaza of the ruins of Dzibilchaltún, about 17kms north of Mérida in northwestern Yucatán. The interesting 2004 paper listing it and other finds, by Gloria Santiago Lastra, is entitled "La Plaza Sur de Dzibilchaltún, Yucatán," and is freely downloadable on the Internet in PDF format at http://www.famsi.org/reports/00006es/00006esSantiagoLastra01.pdf.
Though I find no other species better matching our fossil than those labeled Dallocardia muricata, to me our fossil seems slightly different. Its ridges are slightly less numerous and thicker that those shown on the Internet. Is this because our fossil is several centuries or millennia old, from a time when the ancestors of today's Dallocardia muricata grew shells with fewer and thicker ridges?
I like to think that that's the case, but who knows? Whatever the situation, this little bean-size fossil found among the salt pans gave me the gift of several hours of sleuthing and learning and generally continuing to ploddingly get things figured out.
The big strangler fig that had attracted the spider monkeys was probably the most common fig species in these parts. Strangler figs are those who wrap multiple stems around a "host tree," gradually overtopping the host and out-competing it for sunlight and water, until it "strangles" and replaces the host. A young strangler of the same species as our monkey one stands beside the road between Río Lagartos and Las Coloradas. You can see its multiple trunks, which may or may not have formed around a now-vanished host -- stranglers don't always need a host tree -- at http://www.backyardnature.net/n/15/150111fi.jpg.
Nowadays this roadside strangler also is producing figs, though they're still hard and green. However, when the figs ripen, bats, birds and other critters will devour them so readily that I'm profiling the tree now before it's stripped of its figs. You can see a branch with its large, green but pale-veined, rounded-tipped, leathery leaves, and some green figs, at http://www.backyardnature.net/n/15/150111fj.jpg.
A close-up of a twig tip showing a fig subtended by two green, unusually large "basal bracts" -- these are important identification features-- is at http://www.backyardnature.net/n/15/150111fk.jpg.
In that picture notice the owl-face twig scar at the lower, left, where the stems of two of last season's figs have fallen off. The fact that two figs were produced there instead of one is a good field mark because many species produce single figs at their stems' fig-making places. The green, teardrop-shaped item at the stem's tip is its terminal bud containing new stem growth that will emerge and grow like crazy when the rainy season returns. Just to confirm that the figs are really figs, you can see what they look like when they're broken open at http://www.backyardnature.net/n/15/150111fl.jpg.
This view reminds us that figs aren't really fruits, but rather structures peculiar to fig species inside which very many flowers are packed together rooted along the structure's interior wall and growing toward its open center. Tiny wasps enter a natural hole in the structure, which is called a "syconium," walk around atop the flowers in the syconium's darkness pollinating the flowers, and then leave, carrying that syconium's pollen to another one. In each syconium three kinds of flowers are found:
All these features lead us to what might be the most commonly encountered wild fig in Mexico and much of tropical America, the strangler fig known as FICUS OBTUSIFOLIA. This species occupies a large variety of habitats, from riversides and mangroves to upland oak forests, from southern Mexico south into Brazil. Obviously it's an adaptable species, and in some places it's aggressive. In parts of Mexico it's considered an invasive species. In Spanish usually it's called Amate or Higuera, but those are names likely to be used for any strangler fig.
If only because many forms of wildlife feed on the species' abundant figs, this is an important tree wherever it occurs. Its a fine shade tree, too. The one in the photo stands at a good turn-around point on my biking road toward Las Coloradas. Each week I spend time enjoying its shade, and watching the figs mature little by little. But I know from experience that because of the competition there always is for ripe figs, I'll be lucky to get any at all.
COASTAL PRICKLY PEAR
We've often mentioned that cacti here on the Yucatan's northern coast are unusually interesting not only because of their many kinds but also because many of the species are rare and/or narrowly endemic. Not all of our species fit that mold, however, such as the one shown at http://www.backyardnature.net/n/15/150111op.jpg.
This is the most abundant cactus species in our area, turning up not only in very thin soil atop limestone where few woody species can live, but also in the savanna and fenced-in ranchlands. Sometimes they form extensive, knee-high thickets it's hard to walk through without bloodying your legs. A small patch in a fenced-in ranch area is shown at http://www.backyardnature.net/n/15/150111ou.jpg.
With those flat, beaver-tail-shaped pads, this is obviously a prickly pear cactus, genus Opuntia. However, Opuntia is a big genus, so the challenge is to know which prickly pear this is. I've waited until now to focus on the species because I needed a flower for certain identification. A portrait of its pretty blossom is shown at http://www.backyardnature.net/n/15/150111oq.jpg.
A peep inside the blossom shows that everything is yellow, not with the center tinged with red as with some prickly pear species we've seen. Otherwise there's nothing surprising there, as you can confirm at http://www.backyardnature.net/n/15/150111or.jpg.
The cactus's spine clusters are a little more interesting, with yellow spines aging brown, some of them curving, plus there are bristle-spines, or "glochids," at spine cluster's bases forming upward-bristling crescents on one side of the clusters, as shown at http://www.backyardnature.net/n/15/150111os.jpg.
Also a little curious about this species is that it doesn't scramble across the ground like most prickly pear species we've looked at, nor does arise from a distinctly tree-trunk-like base, but rather in assumes an in-between posture. You can see its base at http://www.backyardnature.net/n/15/150111ot.jpg.
Another good field mark for the species already was shown in the first picture, at http://www.backyardnature.net/n/15/150111op.jpg.
In that picture, notice the pad margins between spine clusters. The margins are slightly sunken in, giving the pad margins a certain "scalloped" look. Most prickly pear pads don't have scalloped margins.
This is OPUNTIA STRICTA, native in various coastal habitats from the US southeastern states and the Caribbean south to Ecuador. However, this is a vigorous and aggressive species, and now has escaped to become an unwelcome spiny invasive in many tropical and subtropical lands across the Earth. As such it's known by several English names, including Erect Prickly Pear, Common Pest-pear and Pest Pricklypear, but the one seeming most appropriate is Coastal Prickly Pear. Here in its homeland it's seldom seen far from the sea.
It seems that most Internet pages dealing with this species are concerned with its status as an invasive. In Australia at one time it infested millions of acres and still is regarded as a "Weed of National Significance." However, now it's largely been brought under control by the release of large numbers of Cactoblastis moths and the cochineal insect, Dactylopius opuntiae, whose larvae feed on the cactus. In Sri Lanka, it's overgrown a 30 kilometer long coastal area in a national park with special ecological importance as a wetland.
Traditionally, Coastal Prickly Pear has been used in various ways medicinally. In Mexico its mashed pads combined with crushed leaves of the Castor Plant have served as treatments for enlarged spleens.
Because in Mexico its natural enemies keep its numbers in check, Coastal Prickly Pear is a good citizen, a retiring species who knows its place and adds charm and diversity to the landscape. Too bad it's such a nuisance when it goes abroad.
NECKLACEPOD WITH ITS NECKLACY PODS
Last November we looked at a certain woody, reclining bush frequently appearing among our coastal dunes and along roads, called Necklacepod, Sophora tomentosa. Our page showing it loaded with long, branch-tip racemes of yellow flowers is at http://www.backyardnature.net/yucatan/sophora.htm.
Back in November the bush offered no hint as to why it was called Necklacepod, but now during its fruiting season it does. You can see a bush-tip cluster of this Bean Family member's dangling legumes constricted between their beans like a bead necklace at http://www.backyardnature.net/n/15/150111so.jpg.
A mature legume with some of its tan-colored, pea-like beans is at http://www.backyardnature.net/n/15/150111sp.jpg.
Another shot showing how the bush's stems lean into and entangle themselves among upright stems of other woody species is at http://www.backyardnature.net/n/15/150111sq.jpg.
Necklacepod's handsome beans are, as the MedicinalPlantsHerb.Com website says, "dangerously emetocatharitc, toxic, febrifugal, stomachic," loosely translated as meaning that if used right they might improve digestion and bring a fever down, but in too large a dosage might bring forth a violent bout of vomiting, or worse. However, elsewhere it's to be read that the Chinese prepare from the plant's roots an "esteemed tonic" that also serves as a diuretic (makes you pee) and a pectoral (helps with lung problems).
Usually when such a plant enjoys traditional use as a medicinal plant the Internet abounds in pages selling it. Not so with Necklacepod, and I suppose that that means its chemicals are so powerful that no one dares sell them, even on the Internet.
HUANO PALMS, TALL & SKINNY
In extreme northeastern Yucatán State at El Zapotal, the isolated protected area administered by the Mexican environmental group Pronatura, there were lots of tall, slender-trunked palms like the one shown at http://www.backyardnature.net/n/15/150111sb.jpg.
That looks a lot like the famous Huano Palm, Sabal yapa, we've met so often in recent years. Huano Palms are common in northern and eastern Yucatan, and that's the species that provided thatch for my hut roof at Hacienda Chichén. Our Huano Palm Page with lots of info and pictures is at http://www.backyardnature.net/yucatan/huano.htm.
But, the palms in our picture from El Zapotal are taller than those normally seen elsewhere. In the picture, notice my friend Willy below them at the bottom right. Are these regular Huanos who in this protected area have grown larger than the harassed and abused ones normally encountered, or something else? I'd heard of a close relative, the endangered Sabal gretheriae, endemic to just a small part of northeastern Yucatan and described for the first time only in 1991, so could this be that? "Doing the botany" to find out, I began with a closer look at the palm's spherical crown with its inflorescences full of tiny, bee-buzzed flowers, shown at http://www.backyardnature.net/n/15/150111sc.jpg.
An important field mark for members of the genus Sabal is that at the bottom of their fan-shaped fronds the stiff petiole, instead of abruptly stopping at the point of attachment, continues on up into the fan, gradually diminishing in width and ultimately curving a bit, imparting a certain twistiness to the frond. Fan palm fronds with such intruding petioles are said to be costapalmate, and you can see that this palm's fronds are indeed costapalmate at http://www.backyardnature.net/n/15/150111se.jpg.
The trunk's petiole scars from fronds lost long ago give the trunks a segmented look, as shown at http://www.backyardnature.net/n/15/150111sf.jpg.
Well, the short story is that these tall, spindly fan palms are indeed our our old friend the Huano, just that by being protected by the good folks of Pronatura they've been allowed to express their mature natures. In other places we are left dealing with the robust and landscape-enhancing but nonetheless not very graceful or dignified forms of mere juveniles.
WILD ROYAL PALMS
Joyously standing in summery, ear-flapping wind in the back of Diego's black pickup truck with flamingo and fish decals artfully applied to its sides, ostensibly we were looking for rare birds for a Finnish birding guest, but my eyes couldn't be taken off the vegetation that rolled by, for here just an hour or so east of Río Lagartos the seasons were rainier and the vegetation higher and lusher, with species not seen farther west. Suddenly there was a whole forest of some old-friend palms, palm compadres I've known for many years as Royal Palms, ROYSTONEA REGIA, but these Royal Palms were doing things that surprised me.
What surprised me was that I'm used to Royal Palms standing regally in straight lines along streets and plantation entry lanes, planted and cared for, as shown on our Royal Palm Page at http://www.backyardnature.net/yucatan/royal-pm.htm.
But these Royal Palms stood shaggily and haphazardly in wild forest, as seen from the back of Diego's famous Flamingomobile at http://www.backyardnature.net/n/15/150111ro.jpg.
A close-up showing the Royal Palm's main field marks is at http://www.backyardnature.net/n/15/150111rp.jpg.
Here's what to notice:
I myself have written that "Royal Palms are native to southern Florida, southeastern Mexico, including the Yucatan, Cuba, the Bahamas and the Cayman Islands. Earlier the Florida populations were regarded as a different species, but genetic studies show that they are not distinct enough to be regarded as a separate species..." so all along I've known that wild Royal Palms should be growing here in the Yucatan. However, during all my years of Yucatan-wandering I've never seen them, so I'd begun suspecting that they were practically extinct here, except where planted.
I'm told that all the Royal Palms in our area occur in that small forest we zoomed through and that all the land there is owned by one person, who recognizes the trees' importance.
FINE-TUNING THE LEATHER FERNS
Back in 2006 during my first visit with Diego I profiled the Giant Leather Fern, Acrostichum danaefolium, which grew robustly and impressively out in the sun-drenched marshes. You can see the fern we looked at then at http://www.backyardnature.net/yucatan/acrostic.htm.
However, two giant leather fern species are listed for the Yucatan, Acrostichum danaefolium and Acrostichum aureum. I was pretty sure that our marsh-dwelling one was Acrostichum danaefolium, but would I recognize Acrostichum aureum if I came across it? The Flora of North America and other technical treatments all appear to be in general agreement about differences between the two species. On fronds of A. aureum, only the outermost segments, or pinnae, produce spores, while on A. danaeifolium the spore-producing pinnae occur throughout most of the frond. Aureum's pinnae don't overlap but danaeifolium's more or less do. And the cells, or "areoles," formed by the smallest veins at the edge of the pinnae are narrow in aureum but broad in danaeifolium.
After paying attention to hundreds of leather ferns in this area it's gradually dawned on me that we do have two distinct forms here, one thriving in full sunlight in grassy marshes, while the other lives in shadowy mangroves. However, the field marks outlined above haven't help at all. The fronds of both species lose pinnae at their bottoms as they age, whether they're spore producing or not, so it's hard to say how much of a frond is spore producing. "More-or-less overlapping pinnae" appeared on both forms. Also,I've photographed areoles" at the edge of the pinnae of the two forms, and they're shown at http://www.backyardnature.net/n/15/150111ae.jpg.
I just don't see that much difference" between them. The different sizes might be accounted for by the camera lens being at different distances from the pinnae. Even drawings of areoles in the Flora of North America don't clearly indicate the differences decribed between them. Maybe this is one of those times when experts generation after generation copy from one another with no one ever checking to see if what's written coincides with reality.
Still, something else said in the Flora of North America, where the situation is described in Florida where the two species coexist, fits perfectly what I find here. That is, "Acrosticum aureum is more frequently found in coastal shaded areas, in saline black-mangrove communities ... Acrostichum danaeifolium grows vigorously in full sun and is common and widely distributed in Florida."
That fits the two "forms" I've recognized here, so I continue to call the much more commonly found marsh-and-full-sun one Acrostichum danaeifolium, and the ones occurring in deep shade and often in standing water in the mangroves now I'll designate as Acrosticum aureum, often called the Golden Leather Fern.
GOLDEN LEATHER FERN
One place to see ACROSTICHUM AUREUM, often called Golden Leather Fern or Mangrove Fern, is beside the pond known as Petén Tucha, the same spot deep inside the mangroves where the spider monkeys dropped unripe figs onto the forest floor. You can see some of my students crocodile watching at Petén Tucha next to a shade-loving Golden Leather Fern standing about ten feet tall (3m) at http://www.backyardnature.net/n/15/150111ac.jpg.
A close-up look at parts of two fronds, wth fertile, spore-producing pinnae at the top and sterile pinnae at the bottom, is shown at http://www.backyardnature.net/n/15/150111ad.jpg.
Golden Leather Ferns occur in coastal mangrove swamps, salt marshes, low hammocks, and along lake and canal margins worldwide in tropical and subtropical regions, including in Florida in the US.
With such a large distribution area it's to be expected that some culture someplace uses Golden Leather Fern medicinally. In Fiji it's been documented as used to promote healthy pregnancies, for sinus problems, sore throat, wounds, elephantiasis, to bring down fever, and to deal with chest pain.
WATER CLOVER FERNS PRODUCING SPORANGIUM CASES
Last November before the natural ponds along the coastal road between Río Lagartos and San Felipe dried up, we looked at water clover ferns growing thickly in one of the ponds, as shown at http://www.backyardnature.net/yucatan/marsilea.htm.
With the ferns in hand, the question arose as to how such an aquatic fern produces and disseminates its spores. Last November I looked for spore-producing bodies -- more technically referred to as "sporangium cases" or "sporocarps" -- on many ferns but found nothing. Now that the pond has disappeared and the ferns look like four-leafed clovers growing on spongy, moist soil, I decided to take another look. You can see what the ferns look like now at http://www.backyardnature.net/n/15/150111mc.jpg.
The clover-like leaves' long stems arise from wiry rhizomes creeping through the mud just below the surface. You can how roots arise from the rhizomes' nodes at http://www.backyardnature.net/n/15/150111ma.jpg.
Water clover's sporangium cases arise at the fronds' petiole bases, and in the above photo you can see green, lentil-shaped items on their own short stems just above where clumps of petioles issue from the rhizome. Those are sporangium cases. A closer look is provided at http://www.backyardnature.net/n/15/150111mb.jpg.
The Flora of North America says that among North American water clovers -- genus Marsilea -- sporangium cases are borne aboveground in all but one species. If those other Marsilea species with aboveground sporangium cases wait until their ponds dry up before producing their fruiting bodies, then we know how most water clovers disseminate their spores: the usual way, via the wind. Our ferns' sporangium cases were held at or just below the mud's surface, but they weren't yet mature. As the ponds continue to dry out I can imagine that not only will the cases' stalks elongate but also the mud will contract as it hardens, leaving the cases high and dry, and exposed to the dry season's hot wind.
The Flora of North America also says that "Species identification is virtually impossible without fertile material." In November we identified our local water clovers as Marsilea vestita because that's the only species known to exist here. Now that we have sporangium cases it's easy to confirm that we really do have Marsilea vestita, because the sporangium cases of other species lack the tiny "hooks" clearly visible on the cases just above where the cases attach to their stalks. Other species may bear various kinds of projections there, but not like these.
This week as I searched for our water clover's sporangium cases, at first I didn't find them, because first I looked where the water had been deepest and had remained standing longer. Only when I went to the edges and where the ground rose because of buried rocks did cases appear. This suggests that our water clovers are producing their sporangium cases now not because of day length or cooler temperatures, but because the water has gone down and soon the ground they're in will be dry.
FEATURED ESSAYS FROM THE PAST:
"Focusing" from the April 18, 2004 Newsletter, at http://www.backyardnature.net/n/p/040418.htm
"Flâneuring in Dzitas" from the March 4, 2012 Newsletter, at http://www.backyardnature.net/n/p/120304.htm
Best wishes to all Newsletter readers,
All previous Newsletters are archived at http://www.backyardnature.net/n/.