January 8, 2012

BOUGAINVILLEA FLOWERS
Bougainvilleas are among the most planted, most appreciated and most beautiful of all tropical plants. They're native to South America but are planted in the tropics worldwide. Down here if you see a woody vine overflowing its arbor or fence, scrambling onto rooftops and even flowing into neighboring trees, and bearing unnaturally large clusters of usually-red flowers that seem to last and last, probably that's a Bougainvillea. You can see a typical planting here at https://www.backyardnature.net/n/12/120108bv.jpg.

Up close, the gaudy clusters resolve into curiously three-sided, 1½-inch tall (4cm) structures, as shown at https://www.backyardnature.net/n/12/120108bw.jpg.

Most folks call that structure "the flower," but it isn't. It's a cluster of three flowers. An actual flower with its subtending bract is shown at https://www.backyardnature.net/n/12/120108bx.jpg.

Bracts are modified leaves and in this picture you can see veins suggestive of the ancestral leaves from which the bracts were modified. Many bracts are so highly modified that the veins don't look like veins, or are nonexistent. Once a wild Bougainvillea's flower dries up and shrivels, a dry fruit appears affixed to the papery bract. The bract catches in the wind and helps the fruit disseminate away from the parent plant.

In the above picture the dark, slender thing arising from the bract's base is the flower's slender calyx, which is red without and white inside. Bougainvillea flowers bear no corollas, but you can see that the calyx does a good job mimicking one. Notice that the calyx bears five lobes like a normal corolla. A longitudinal section showing the flower's sexual parts inside the cylindrical calyx tube can be seen at https://www.backyardnature.net/n/12/120108by.jpg.

There the stamens' sandgrain-like, yellow anthers reside atop long, pale, hairlike filaments of unequal lengths joining at their bases. These and other flower features confirm the Bouganvilleas's membership in the Four-O'Clock Family, the Nyctaginaceae, which is a family mainly of the tropics and subtropics, and predominantly in the Americas.

Bouganvillea taxonomy is a mess, the experts defining as few as four species in the genus BOUGANVILLEA and as many as 18. There's been so much hybridizing between species, resulting in over 300 named cultivars, that assigning a species name to a particular plant is hard to impossible, and probably misleading. In traditional, outdated taxonomy, however, the species shown here would be Bouganvillea glabra.

Bouganvilleas are named after French Navy admiral and explorer Louis Antoine de Bougainville.

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LOOKING AT LICHENS
At https://www.backyardnature.net/lichens.htm I write that "Lichens are not plants. They are 'composite organisms' made up of two, or maybe three, completely different kinds of organisms. It's as if you combined an animal such as a dog with a plant such as an oak, maybe with a fungus thrown in as well, and ended up with something very different from animal, plant or fungus. Something that was its own thing, with its own identity and manner of being." Lichens are composed of a fungus plus either or both a photosynthesizing alga, or a cyanobacterium -- a kind of photosynthesizing bacterium.

At the above link also I've drawn what a lichen's algal cells with fungal hyphae wrapped around them might look like at a microscopic level.

We have lichens here, though they're not as conspicuous as in rainier places or at higher elevations. They're especially noticeable nowadays because as the dry season advances more and more deciduous trees lose their leaves letting in more light, plus in the dry air the light is so dazzlingly bright that in protected, usually shaded spots where lichens are likely to show up there's more light to see them with.

Traditionally lichens have been divided into just three growth-form types: Crustose (crust- or paint-like), foliose (leafy) and fruticose (branched). Nowadays other lichen types are recognized, such as filamentous (hair-like), leprose (powdery), squamulose (made of scale-like structures) and gelatinous.

One place where they're particularly obvious is on the smooth trunks of dry-season-leafless Frangipani trees, as at https://www.backyardnature.net/n/12/120108lk.jpg.

That picture shows a classic foliose species, with flat, thumbnail-size thalli -- "thalli" being the plural for "thallus," which in spore-producing plants refers to the plant body not differentiated into stem and foliage. This looks a lot like Parmatrema tinctorum, commonly found on neotropical garden and roadside trees, but I can't be sure. That species mainly reproduces vegetatively with tiny, sandgrain-like structures called isidia, which simply crumble off the thallus, then produce new lichens where they end up.

At https://www.backyardnature.net/n/12/120108ln.jpg you see another foliose species with similar thalli, but this one's fungal component produces little cup-fungus-like fruiting bodies known as apothecia. Fungal spores from the apothecia blow away, fungal hyphae germinate from the spores and grow across a substrate, and if they encounter the right freely growing alga or cyanobacterium cells, the hyphae start growing around the cells, and a new lichen is born.

Mostly in humid tropics over 800 lichen species are known to grow on leaves. Technically leaf-surface-growing lichens are known to be "foliicolous." Many other kinds of organisms also live on leaves, such as mosses, fungi, bacteria, etc., and as a group the various organisms are said to be "epiphylls." The leaf-surface habitat itself is called the "phyllosphere." One of our foliicolous lichens appears at https://www.backyardnature.net/n/12/120108li.jpg.

An arty close-up of the above lichen bodies is at https://www.backyardnature.net/n/12/120108lj.jpg.

Exploring for lichens here is frustrating because there's no way the amateur can identify them. For example, I'm not even sure that this is a lichen: https://www.backyardnature.net/n/12/120108lo.jpg.

It certainly branches like certain foliose lichens, but they're tiny and their thalli are so slender. And then there are such things as is shown at https://www.backyardnature.net/n/12/120108lm.jpg.

That might even be a slime mold.

One morning this week I spent two solid hours exploring the smooth trunk of a leafless Frangipani tree. It was exhilarating, frustrating, and an awful lot of fun. Folks up North can experience similar moments, even in the winter, and up there field guides can be acquired to help. Check out the Amazon.com ads on my Lichen Page linked to at the beginning.

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MOSSES, TOO
The same general situation exists for mosses, too. We have a few but identifying them is hopeless. Look at https://www.backyardnature.net/n/12/120108ms.jpg.

Those live on a limestone windowsill up at the old colonial church where I used to live, and stand about ¼ inch (6mm) high. A neat thing about the photo is that you can see the pale, cellophane-like caps, or "calyptra," perched atop the stalked, spore-bearing "capsules."

To identify this moss we'd need not only technical literature we don't have, but also a microscope, or at least a powerful jeweler's loupe, in order to see cell shape and such. Up North mosses are more numerous and varied than here, and you have some fine books to help you along. Such books are linked to on my Moss Page at https://www.backyardnature.net/mosses.htm

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A THEORY OF FIG-SEED DISSEMINATION
We've often encountered strangler figs. Their page is at https://www.backyardnature.net/mexnat/strangle.htm.

An amazing thing about strangler figs is that their tiny seeds germinate on the limbs of other trees, thus the plants start out as epiphytes, but they send roots to the ground and become rather like vines, but meanwhile they're also growing upward and overtopping the host tree. As the roots merge around the host's trunk, eventually the fig out-competes the host for sunlight, water and nutrients, "strangling" it, and eventually takes its place.

Long ago I read somewhere that strangler fig seeds get to the host-tree branches via birds who've been eating the fruits. The fruits are juicy with sticky latex, so seeds stick to the birds' bills. When the birds fly to another tree they clean their bills on the branches they're perched on, sowing the seeds.

Currently our Chinese Banyan, which is an introduced strangler fig, is producing prodigious numbers of garbanzo-bean-size figs, which attract large numbers of birds who gorge on them. Eating so much fruit, the birds' poop becomes watery. The birds drop their poop frequently, splattering everything below them. Such seed-filled, dried-out poop on leaves is shown at https://www.backyardnature.net/n/12/120108pp.jpg.

It may be that birds cleaning their beaks on candidate host trees sow the seeds there, but I'm thinking that so many seeds get sown by birds with the runs that beak-sown seeds must be a minority.

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COTTON BOLES OPENING
Each day the Tree Cotton trees look a little scruffier as leaves dry and curl up, and eventually fall off for the dry season, and each day more bolls open to release fluffy wads of beige-colored cotton, as shown at https://www.backyardnature.net/n/12/120108tc.jpg.

At the lower right in that picture there's an immature, green fruit, or boll, mostly enclosed in the flower's three, large, deeply incised bracts. Most bolls produce four clumps of cotton, each clump produced in an ovary's cell, or carpel, though some bolls produce only three or as many as five. Each clump contains five or less often four seeds, rarely six. Thus each boll produces on the average 4x5=20 seeds, which are the size of grape seeds, hard and dark, and difficult to separate from the cotton.

The trees bear hundreds of bolls so everyone dropping by the hut nowadays is encouraged to carry seeds home and plant them, for this is a genuine "Maya heritage" species, as is explained on our Tree Cotton page at https://www.backyardnature.net/yucatan/treecott.htm.

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ELEPHANTEAR FRUITS
In last November 20th's Newsletter we looked at the 14-inch tall (35cm) "flowers" of an Arrowleaf Elephantear standing in front of the hut. "Flowers" is in quotation marks because the structure thought of as a flower actually is a cluster of many flowers. Pictures of the plant and "flower" are still online at https://www.backyardnature.net/yucatan/elephant.htm.

Since then several such "flowers" have appeared and withered back, and they're still being issued, so this week I succumbed to the urge to cut open a "flower's" bottom compartment to see what was going on there. You'll remember that in this species the spike emerging from the spathe bears many male flowers while, below, the spathe completely wraps around the part of the spike bearing females flowers. You can see two lower compartments with the near sides cut away at https://www.backyardnature.net/n/12/120108ee.jpg.

In that picture the flowering spike, or spadix, on the right is still in the flowering stage. You can see that the upper part of the spadix bearing male flowers is different from the lower part bearing female flowers. The male items are angular columns composed of fused anthers while the lower, oval, pinkish, female things are immature stigma heads atop unseen ovaries. Below the ovaries -- that's smelly, mushlike decaying material working with maggots...

At the left is a much older flower. We'd expect to find fruits developing in it, like grains on a corncob, but its spadix also is covered with decaying, stinking, maggoty stuff.

The deal is that under natural conditions fruit and seed production in Arrowhead Elephantear is extremely rare. That's because of a circumstance known as "extreme protogyny," which means that the female flowers mature and stop being receptive to being pollinated about 20 hours before the male flowers' stamens mature enough to produce pollen. This strategy hinders self-pollination, and when you just have a couple of plants growing well apart, and usually one or the other isn't flowering, pollination becomes hard to impossible. The decaying material, then, consists of female flowers that never got pollinated, and so aborted.

If we had enough plants here for the flowers to get properly pollinated, the resulting fruits would mature 40-60 days after pollination. Fruiting heads typically bear between 200-300 berry-type fruits.

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STRATOCUMULUS STRATIFORMIS CLOUDS
One mid-afternoon this week a blanket-like cloud bank moved in from the east. It'd been a sunny morning so air next to the ground was warm. The warmth bubbled upward in convection currents, disturbed the cloud cover, and resulted in the cloud formation shown at https://www.backyardnature.net/n/12/120108ss.jpg.

To a Northerner that might look like a cold, late afternoon, winter sky but in fact when I took the picture it was warm, humid and balmy. Such a cloudy sky was a little unusual so far into the dry season, but not too much so. It's a thin layer, or stratum, as evidenced by the cloud-blobs' edges translucing with sunlight from above. Since the cover is continuous, even though it's irregular, I figured it was a kind of stratus cloud, and since its shiny-sided lumps looked like crammed-together cumulus clouds, I guessed that the whole formation might be a kind of stratocumulus, and that turned out to be so.

The World Meteorological Organization lists three "species" of stratocumulus: One with its lumps towering upwards; another with lens-shaped lumps, and; one described as "sheets or relatively flat patches of stratocumulus." The last one is ours, and that's STRATOCUMULUS STRATIFORMIS.

A similar-looking cloud type is that of Altocumulus stratiformis, but that type forms higher up. Its lumps in general appear smaller and the stratum is thinner, with sunlight above it passing through more easily.

In the North, general wisdom is that Stratocumulus stratiformis clouds form from the rising and breaking up of low sheets of stratus clouds, and rarely produce rain. Ours formed at the head of a rainless, dry- season front. The sky just behaves differently here.

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ON LOSING LAST WEEKEND'S PICTURES
Last Sunday morning, as usual, I biked to Pisté to buy fruit and wander around looking in people's backyards for interesting plants. I even pedaled up to Xocempich and wandered around there, getting some fine pictures of surprising new species. I couldn't wait to get the images into the computer and start thinking about them.

But, something went haywire as the images transferred from camera to computer, and I lost them all. I felt pretty sour.

Then I thought about it. What I really like about these picture-taking Sunday mornings is the hunt for new things, and all the learning, thinking and writing that come afterwards when I'm figuring out what I've taken pictures of. I'd already finished the hunt, and the Universe still beckoned with an infinity of images to be taken, of thoughts still to be summoned, and art still to be practiced. Instead of losing something I'd received a new offer to hunt more, think more, write about something different...

Here's the way it is with the pictures I send you: My attention is drawn, say, to the Bougainvillea we looked at above. When I took those pictures it was a soft, balmy morning. Something in the sunlight charged the flowers' crimson color with such dazzling vivaciousness that I knew no computer-screen image could ever convey the experience's feeling, but maybe it could hint at it, so I tried.

Back in the hut on and off for several days I worked on the Bougainvillea's images and figured out what I wanted to say about them. On Sunday morning at dawn when I click SEND in my Newsletter program, the Bougainvillea's gaudy splashes of red gush from my computer eventually onto computer screens all over the world, in people's living rooms, office cubicles, on kitchen tables, in cars sitting outside wireless-equipped libraries, maybe even in one or two thatch-roofed huts like the one these thoughts are being thought in and the words are being typed in.

What a pleasure to be part of this on-going thing that you and I are part of, this tiny, evolving, mutually inspiring coming-to-see-things blossoming we're experiencing right now. And none of this depends on my having any particular set of images. The Universe is so full of potential images and thoughts we can hardly imagine it.

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Best wishes to all Newsletter readers,

Jim