February 11, 2018
NEGRITA'S FAVORITE WEED-NIBBLE
Often the rancho's dogs can be seen eating dirt and nibbling on vegetation. One assumes the dirt provides minerals that may be missing in their regular dogfood diet, and the plants they eat might be medicinal. For awhile I've been noticing that Negrita the black dog never passes a certain weed without stopping for a nibble, so this week as we approached that weed I got the camera ready so you can see her at work at http://www.backyardnature.net/n/18/180211ng.jpg
In the past I couldn't identify to species level the typically flowerless and fruitless herbs eaten by dogs, and without an identification there's nothing noteworthy about saying that a dog has eaten a weed. This time, however, when I went to see what she'd been eating, it turned out to be a species we looked out just last month, the Composite or Sunflower Family member Aldama dentata, whose page is at http://www.backyardnature.net/mexnat/aldama.htm
So, what does Aldama dentata offer that's so seductive to Negrita that she can't pass it without nibbling on it? On the Internet I find that anthropologist Alejandro Magaña found the Chontal Maya in Mexico's Tabasco state fusing Aldama dentata to deal with high cholesterol. But that didn't seem likely to account for Negrita's fondness of the plant.
Crushing a leaf brought forth no particular odor, and it tasted like any ordinary leaf. However, in tasting it, I did experience one notable sensation, and that is that the leaves were very rough on the lips and tongue. Looking at a leaf surface with a hand lens revealed what's shown at http://www.backyardnature.net/n/18/180211nh.jpg
At the microscopic level, the leaves are armored with stiff, sharp, broad-based hairs looking like they could rip into the soft belly of a munching caterpillar or, for that matter, discomfit any leaf-munching invertebrate. Maybe these sharp hairs would wreak havoc on a dog's population of intestinal worms.
At the Pets.WebMD.COM webside I found a discussion on why dogs eat grass. That topic might bear on Negrita's behavior because often grassblades are similarly equipped with sharp, stiff hairs. It's suggested that dogs may eat grass to cause themselves to vomit, though less that 25% of dogs who eat grass vomit after "grazing." Other suggested reasons for eating grass included improving digestion, treating intestinal worms, or fulfilling some unmet nutritional needs, such as the need for fiber. Also, possibly certain dogs simply like how grass tastes or feels.
Of those possibilities, I think the most likely reason for Nigrita habitually eating scratchy Aldama dentata leaves is to help control intestinal worms.
Along partially shaded pathways and trails, exactly at the edge of dirt kept bare by passing feet, very often a certain scraggly looking herb with ankle- to knee-reaching spikes of widely spaced, tiny, blue flowers appear, sometimes abundantly. When shrill morning sunlight cuts in from the side, these pathside plants look like what's shown at http://www.backyardnature.net/n/18/180211sv.jpg
Up closer you see that the herbs display certain features of the Mint Family, as seen at http://www.backyardnature.net/n/18/180211sw.jpg
Moreover, though the herbage isn't particularly fragrant, the herbs' stems are squared in cross section as they should be in the Mint Family, and the plants' opposite leaves are toothed along their margins like Spearmint, as shown at http://www.backyardnature.net/n/18/180211sy.jpg
Up close, the flowers also look typical of the Mint Family, their corollas with their bilateral symmetry shaped like little dog heads, as seen at http://www.backyardnature.net/n/18/180211sx.jpg
By this time we're pretty sure we have a member of the Mint Family, the Lamiaceae, and when the corolla's top lip is peeled back to display the stamen arrangement, not only is the Mint Family more or less confirmed, but also it's realized that often we've seen this stamen arrangement on an important genus in the Mint Family, as seen at http://www.backyardnature.net/n/18/180211sz.jpg
Two stamens hug the fork-tipped style as it arcs up beneath the corolla's down-curving top lip, the stamens' filaments structured so that in-coming pollinators push a kind of "lever" causing the stamens' pollen-laden anthers to bend down and daub the pollinator's rear end with pollen. In the above picture you can barely see the nearest filament developing some kind of "lever" just before it disappears into the corolla's tube.
The configuration speaks of a species of sage, genus Salvia, though this is the smallest-flowered sage I've ever seen. It's SALVIA MISELLA, in some publications mentioned as Salvia riparia, in English known variously as Tropical Sage, Florida Keys Sage, and Southern River Sage. The two latter names are mostly used in Florida, where it appears in the state's southern half. The species also occurs on islands in the Caribbean, throughout Mexico, and south to Venezuela and Peru.
In our environment, Tropical Sage's main job seems to be to occupy and protect from further erosion much-abused soil, but I read that in Florida it's valued as an attractive ground cover in semi-shaded locations. It's stated that it flowers throughout most of the year, though here I've not seen it putting on a show until right now.
Enmeshed among weeds overgrowing one of the rancho's fences, in a fairly shaded spot, was a head-high plant so spindly and leggy that it was hardly visible amid all the visual clutter. I'd not notice it until now, but now its small, white flowering heads caught my attention. You can see a sprig removed from the weedy tangle at http://www.backyardnature.net/n/18/180211is.jpg
Notice that leaves arise opposite one another on the stiff, slender stems, and the leaves themselves are strongly three-nerved. The flowering heads reside at the tips of long, slender, stiff peduncles. A tip is shown close-up at http://www.backyardnature.net/n/18/180211it.jpg
There you see three flowers of the type produced in the big Composite or Sunflower Family, the Asteraceae. When we think of that family usually we visualize something like sunflowers or asters, where each flower is composed of two kinds of florets -- petal-like ray florets surrounding and "eye" composed of cylindrical disc florets tightly packed in the flower's center. Some composite flowers, however, such as those of dandelions and lettuce plants, only produce ray florets, while others, such as the eupatoriums and horseweed bear only disc florets. In the picture we see three flowers consisting only of disc florets. The narrow, green, sharply tipped items beneath each cluster of disc florets are bracts constituting the flowers' involucre.
At http://www.backyardnature.net/n/18/180211iv.jpg we see the top of one of these clusters showing tiny, white, disc-floret corollas, each with five back-turned lobes. The Composite Family is so huge and diverse that for a solid identification often you need to break open a flower to see how things are constructed inside. This plant's interior anatomy is on display at http://www.backyardnature.net/n/18/180211iu.jpg
Good field marks to notice are that the platform on which the disc florets arise, instead of being flat or somewhat convex, is tall and slender, or "columnar." The cypsela-type fruits are black at maturity, and the base of each floret is partly surrounded by a greenish, scoop-like bract called a palea.
With all these fine field marks it was easy enough to determine that our plant is ISOCARPHA OPPOSITIFOLIA, distributed from Texas south through Mexico and Central America to northern South America. Occurring in Texas, it's been bestowed with the English name Rio Grande Pearlhead. However, the Rio Grande lies at the extreme northern fringe of this widely distributed tropical American plant, so here we'll just call it Pearlhead.
Though any weed can be considered as a first responder working hard to save and bring back to life injured natural communities and mistreated soil, the only compliment I can find humans giving it is that it's attractive to certain pollinators.
In the garden a half-heartedly vining herb turned up almost hidden inside a washing-machine-size, dense clump of lemongrass. I pulled out a branch tip, held it against the sky so its details could be seen, and got the photograph at http://www.backyardnature.net/n/18/180211tg.jpg
It's a curious looking plant, with such fuzzy items at the ends of long stems, and elm-tree-like leaves on long, hairy petioles. In fact, the whole thing was exceedingly hairy, and once I'd made contact with some of the hairs I realized that they stung like a nettle's stinging hairs. You can see the stingers amid non-stinging hairs on the stem at http://www.backyardnature.net/n/18/180211th.jpg
The fuzzy balls, which were three-parted fruits, also bristled with sharp hairs, as seen at http://www.backyardnature.net/n/18/180211ti.jpg
The dark, three-armed item in the center is a branched style bearing stigmas. A side view of less mature fruits, a small flowering head of minute, purplish male flowers, and an expanding purplish leaf is shown at http://www.backyardnature.net/n/18/180211tj.jpg
And a shot of some mature leaves is at http://www.backyardnature.net/n/18/180211tk.jpg
We met something very similar to this back in Texas, and you might enjoy seeing how our current plant compares with it. The smaller Texas plant, which bore much narrower leaves but similarly hairy fruits, can be seen at http://www.backyardnature.net/n/h/noseburn.htm
Our Texas plant, a member of the Euphorbia or Poinsettia Family, the Euphorbiaceae, wasTragia ramosa, in English sometimes called Branched Noseburn. Our Yucatan garden plant turns out to be TRAGIA YUCATANENSIS, which I call Yucatan Noseburn, though I've seen no one else using that name.
Yucatan Noseburn seems to be common in the Yucatan Peninsula. A very similar species, Tragia glanduligera, is of much greater distribution, from Texas south through eastern Mexico into Guatemala. From pictures on the Internet I can't see any difference between the two species, though the Flora of North America describes the inflorescences of Tragia glanduligera as prominently bearing "stipitate glands," or glands atop stiff stalks, or "stipes," and our garden plants don't have those.
Little information is available for this species, but it's a pleasure to meet, if only because of its stinging hairs and funny name.
DOUBLE-TAKE: TWO DOGS & A BOA
Sometimes two views of completely different situations mingle in the mind to create insights beyond what you get by considering the situations separately. Here's what I mean, starting with one of this week's events:
The dogs Katrina and Negrita run with me each morning as I jog. If turning a corner we find a squirrel or coati on the road ahead, both dogs instantly shoot forward at full speed, although they know they can never outmaneuver such animals when they dive into the scrub at the trail's edge. Katrina is the larger, older dog, while this is Negrita's first dry season as a grownup. Katrina at top speed runs like a bouncing rubber ball; Negrita speeds past her like a bullet, with no wasted motion.
But, though Negrita always arrives first, she never knows what to do once she's gotten there. Katrina is the one providing ideas and leadership.
And, isn't that just how things usually are? I explain it to myself that this is Nature's way of increasing diversity. It's not enough to have sloppy runners and gifted runners, but also in each category there must be smart ones and unimaginative ones, as well as big and little ones, and some with inherited or learned handicaps, and some with good luck or bad, on and on, until the possibilities become astronomical.
That's the first insight from one of this week's observations -- a little one, but at least worth thinking about. Now the second:
On my fruit-buying bike trip to Temozón last Sunday I came upon a Boa Constrictor as thick as my arm. It'd been hacked to death with a machete and pulled to the roadside for display. It was beside one of the big, new papaya plantations springing up around here, so probably the boa had grown thick by feeding on our abundant, mole-like Tuzas (they're pocket gophers), who eat tree roots, including those of papaya trees, killing them.
So, this week's second insight -- which I already knew but was glad to be reminded of -- was that there's no natural law prohibiting the destruction of beautiful, useful beings, not even by the very ones who most benefit from the destroyed thing's services.
So, a deeper insight compounded from mingling the two separately gathered insights is this: Though Nature uses all kinds of tricks to compound Her creations' diversity, She's not particularly concerned about individual destinies amid all that diversity. To Her, what's important is the creation of Her art gallery but, except in a general, non-personal way, She's unconcerned about Her individual paintings on the wall. Also I've known this for a long time, but it's good to be reminded of it as well.
We individual beings don't like to think of ourselves as belonging to the same category as that well meaning but hacked-up boa along the road. One craves some kind of justice. Well, my thinking is that basic ecological principles interpreted as Earthly-written Bible verses suggest that in the end Nature does grant us some kind of justice.
For, if enough papaya plantations kill enough papaya-tree-protecting wildlife, and if enough water is pumped from the aquifer in this too-arid-for-papaya-growing climate, and if enough insecticide, fungicide and such is dumped into the environment, eventually such a desert will result that even the plantations won't survive. In other words, Anyone so ignorant and unfeeling as to destroy the environment they depend on, shall themselves face extinction.
And that seems like proper justice.
Best wishes to all Newsletter readers,
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