December 23, 2012

LEAFCUTTER ANTS IN THE COMPOST
Earlier I mentioned that our Texas Leafcutting Ant, ATTA TEXANA, had ravaged my beet bed. That story and others, with pictures, is at https://www.backyardnature.net/n/a/leaf-cut.htm.

Since writing that I've gained much unwanted experience with these ants. They cut the tops off many of my Japanese Radishes before I discovered them and sprayed diesel fuel around the raised bed -- a trick I learned from the Maya in the Yucatan. Later they got every leaf of my Tat Soi. They choose one target kind of plant and go after it, ignoring other crops you'd think they might prefer.

I can halfway deal with them by spraying around the raised beds. However, now that they're attacking the big garden it's harder. At first I sprayed all around the big garden, something I disliked very much because this diesel fuel is disgusting stuff. However, I've been planning on eating from that garden and if the ants take it all it's a hard blow.

One day somehow they found a way across my diesel barrier and overnight dug tunnels inside the garden, right beside my turnip patch, and began ravaging the turnips. I dug up their nest and thought I had them controlled, but then the next morning new tunnels appeared in the center of the turnip patch. I sprayed a little but finally realized that I was creating more mess with that diesel fuel than it was worth, so now I just let the ants have what they want. As I write this they are gradually destroying my house-size patch of turnips.

One day this week I was saddened to see a line of leaf-carrying ants in my spinach bed, for I'd hoped they might ignore that crop. However, as I searched for where they were working I found that the line passed through the spinach and beyond, across the entire garden, through the fence and out of the garden, into the compost bin. They were dissecting the rinds of winter squash recently deposited there. You can see some at work on a rind at https://www.backyardnature.net/n/12/121223lc.jpg.

It would be easy to kill off the colony with ant poison, but I have my own reasons for not doing that.

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ASHE JUNIPER'S CLOUDS OF POLLEN
My shoulder brushed an Ashe Juniper's branch and a big puff of powdery stuff clouded from the tree. I stepped back, got the camera ready, shook a branch, and got the picture shown at https://www.backyardnature.net/n/12/121223jw.jpg.

I'd been expecting this because for the last few weeks abundant, pale, 1/8th-inch high (3mm) male cones have been appearing at the tips of the junipers' branchlets, as shown at https://www.backyardnature.net/n/12/121223ju.jpg.

A close-up of some pollen-producing male cones is at https://www.backyardnature.net/n/12/121223jv.jpg.

Each brown, triangular scale on the male cones is a sporophyll subtending two pollen sacs. A sporophyll is a modified leaf bearing sporangia or, in this case, pollen sacs. I nipped off the top of a male cone so you can see the spherical, yellow pollen sacs as seen beneath the dissecting scope at https://www.backyardnature.net/n/12/121223jy.jpg.

In that picture pollen grains from a ruptured sac coat the sporophyll scales.

If Ashe Juniper male cones are producing prodigious quantities of pollen these days there must be receptive female cones in the vicinity. In contrast to the very conspicuous male cones, you have to look a bit before you find the females nestled down among the junipers' scaly leaves. You can see one at https://www.backyardnature.net/n/12/121223jx.jpg.

Female cones also consist of pairs or whorls of sporophyll scales, except that in their case the scales subtend ovules. It's interesting that at this early stage of development already the future fruit is whitish with the frosty covering referred to as glaucescence. On our Ashe Juniper page at https://www.backyardnature.net/n/w/ashe-jun.htm we show very glaucous immature fruits as they appeared in September. You can see that on the mature fruits in December the glaucescence persists, at https://www.backyardnature.net/n/12/121223jz.jpg.

Nowadays on sunny, windy days the air is full of juniper pollen and some people tell me that for them it's a time for sneezing and having watery eyes.

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DAMIANITA
Down on the cobblestone terrace next to the Dry Frio River behind the cabin there are plants not found elsewhere in the neighborhood because rainwater passes through the cobbles creating extremely dry growing conditions atop them. Trees are sparse and only plants adapted to desert conditions grow there. One of those plants I've not seen beyond the terrace is the dense, much branched, knee-high, evergreen shrub bearing mothball-sized fruiting heads shown at https://www.backyardnature.net/n/12/121223ch.jpg.

You can see how the heads are held above the foliage on long, slender peduncles at https://www.backyardnature.net/n/12/121223ck.jpg.

Up close the heads bear achene-type fruits topped with stiff, brownish hairs serving as parachutes for wind dispersal exactly like so many species in the Composite or Sunflower Family. It's a little surprising that this woody bush is a member of the Composite Family because the vast majority of composites are herbaceous. A close-up of a head, almost looking like a brown Dandelion puffball, is at https://www.backyardnature.net/n/12/121223ci.jpg.

Even more surprising for a Composite Family member is what the alternate (one leaf per stem node) leaves look like, shown at https://www.backyardnature.net/n/12/121223cj.jpg.

Those sharp-tipped leaves are a little less than half an inch long (10mm), round in cross section, somewhat succulent, and heavily equipped with oil glands. The glands come as no surprise if you brush against the shrub and smell the strong fragrance that erupts from the plant. It's a slightly medicinal odor, like you might expect from soured juniper berries, if juniper berries soured.

This interesting shrub is known by its Spanish name, Damianita. It's CHRYSACTINIA MEXICANA, its species name reflecting the fact that it's mostly Mexican in distribution, widely occurring in thin soils on limestone outcrops and desert plains in 16 northeastern and central Mexican states, extending into the US only in southern New Mexico and southwestern Texas. Damianita produces small, yellow flower heads that, according to pictures on the Internet, can be much more numerous than the few fruiting heads on our bush. In fact, Damianita can be so pretty in flower that many gardeners in the arid southwestern US plant it where they need something attractive that can survive long droughts in full sunlight, and some coldness. Damianita can be propagated in the garden either by seeds or softwood cuttings.

When you meet such an aromatic plant you can bet that it has fame as a traditional medicine, and that's the case with Damianita. A tea of its stems and leaves is used in Mexico for treatment of skin infections and respiratory ailments.

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SPIKERUSH
In standing, shallow water in a stagnate pool beside the little Dry Frio River below the cabin you can see the spiky little plant shown at https://www.backyardnature.net/n/12/121223el.jpg.

Comparing the size of the plant to the Sycamore leaf floating beside it you can see that the plant is only about seven inches tall (18cm). The little conelike things atop the stems are spikelets composed of scales. Each scale at arises below a flower's sexual parts or mature achene-type fruit -- achenes being dry, one-seeded fruits that don't split open at maturity. A spikelet is shown close up at https://www.backyardnature.net/n/12/121223em.jpg.

In that picture some of the lower scales have been pulled away to reveal the black achenes inside them. A close-up of an achene next to its millimeter scale is at https://www.backyardnature.net/n/12/121223en.jpg.

Note that the black achene is topped with a pale, caplike item. That's called a tubercle and it's the much-expanded base of the style, a style being the neck between a flower's ovary and its pollen-gathering stigma. Tubercles come in many shapes and sizes and are much used when identifying to species level. Also note the bristles arising at the achene's base. Bristles also are typical, and their presence, number, length and color are similarly used for identification to species level.

You've surely seen many of this kind of plant, especially in wetlands. They're commonly referred to as spikerushes and spikesedges and about 120-250 spikerush species are recognized, depending on your expert. The species occur nearly worldwide, mostly in aquatic and wet-soil situations. Most species are larger than the one in our photograph. Spikerushes are members of the Sedge Family, the Cyperaceae. The Water Chestnut is a spikerush. Fifteen spikerush species -- all members of the genus Eleocharis -- are included in Shinners & Mahler's Flora of North Central Texas, and I figure we may have about that many here.

Our spikerush keys out to ELEOCHARIS GENICULATA, which doesn't really have a good common name, since it's not commonly noticed and talked about. The species, an annual, is widespread in wet areas in the Americas, Asia, Africa, and some Pacific Islands.

Among its main field marks distinguishing it from similar spikerush species are; its small size; its black mature achenes; the achenes being lens-shaped in cross section, not three-cornered, and; the low, broad tubercle atop the achene being very distinct from the achene itself.

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WITCH'S BUTTER
Periodically I walk across the field of cobbles forming a low terrace just above the little Dry Frio River running behind the cabin. I like that area because it's an extreme environment -- one where soil can't form atop the cobbles, where even Ashe Junipers have trouble taking root -- so it's a good place to find organisms unusual for this area, and with unique adaptations. For example, our impressive, agave-like Sotols grow best in these cobble fields, as well as the knee-high agave called Lechuguilla, which is abundant in the vast Chihuahua Desert to our west in Mexico, but which until now, here, I've found only in these cobble fields.

So, in an open area in this field of cobbles with Lechuguillas and Sotols growing all around, on certain areas of packed sand I found bunches of dark green, gelatinous stuff looking like freeze-damaged lettuce, as shown at https://www.backyardnature.net/n/12/121223nc.jpg.

My first thought was that it was some kind of green, photosynthetic jelly fungus, but I couldn't remember anything like that. Then I thought it was some kind of herb killed by our recent freeze, but this thing covered the ground over a very large area, and I knew that just a week ago there'd been no herb there, and none of this green, squishy, stuff, either.

Slowly my brain crunched the data and with a little computering the mystery revealed its identity.

It's a kind of photosynthetic bacterium -- a cyanobacterium. It's NOSTOC COMMUNE, going by such evocative English names as Witch's Butter, Star Jelly and Mare's Eggs. It's found nearly worldwide, though only in certain habitats. The Wikipedia page says that it's "able to survive in extreme conditions in polar regions and arid areas. It is a terrestrial or freshwater species and forms loose clumps on soil, gravel and paved surfaces, among mosses and between cobbles." And between cobbles in an arid area is exactly what we have.

In Plant Kingdom class in college back in the early 1970s we were taught that Nostoc was a blue-green alga. One reason that Witch's Butter is no longer considered to be an alga is that its cells contain no nuclei or internal membrane systems. Instead of undergoing standard mitosis, the cells simply divide into two with none of that chromosome-lining-up business going on in the dividing cells of higher organisms. Also, Nostoc's photosynthesizing pigments are scattered loose in the cells' cytoplasm, not organized into chloroplasts as among the algae. One reason Nostoc can survive in our sun-baked cobble field is that it also contains pigments that absorb long- and medium-wavelength ultraviolet radiation.

Not only can Nostoc photosynthesize, but also it can "fix" atmospheric nitrogen -- convert the abundant but mostly unusable nitrogen in our air into forms absolutely necessary for itself and other organisms.

I read that Witch's Butter is eaten in many countries. In China it's known as "Facai" and a dish made from it is traditionally served at the Lunar New Year.

This is the second cyanobacterium we've run into here, the other being a filamentous species known as Oscillatoria, and I'm getting the feeling that I need to start paying more attention to this group.

In the book Oceans and human health: risks and remedies from the seas, I Steward and IR Falconer write:

Steward and Falconer go on to say that in the history or Life on Earth, cyanobacteria created the conditions in the Earth's early atmosphere that directed the evolution of the higher oxygen-using organisms that came after them, and that they are very important contributors to the planetary biosphere's current carbon and nitrogen budgets.

That's saying a lot for a group of organisms that during my years in college wasn't even recognized as other than just a group of primitive algae.

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A PENNATE DIATOM
While scanning a drop of water from a shallow, stagnate pool beside the little Dry Frio River behind the cabin I was about to give up on finding anything interesting when I noticed that at a size much smaller than I was focusing at many slender, pointed items were suspended in the water. I increased the magnification as high as I could and saw what's shown at https://www.backyardnature.net/n/12/121223dm.jpg.

There were jillions of them, obviously important in the pool's ecology, and I didn't know what they were. Hours of work with an image-search engine finally turned up a picture matching what's shown above. It's one of many kinds of diatom, though I can't say which one it is. A page on diatoms produced at Berkely University says "It is a brave thing to identify a Diatom by genus. It is a foolhardy thing to attempt its species."

Diatoms are have true cells with defined nuclei enclosed in nuclear membranes, and they photosynthesize with chloroplasts, so they are classified as algae, which are plants, The largest diatoms are only about 2mm long (1/16+ inch long). The one about is about 200 micrometers (0.008 inch) long.

Traditionally diatoms have been divided into two orders:

The one above is a pennate diatom.

Diatoms constitute one of the most common types of phytoplankton -- freely floating, microscopic, photosynthesizing organisms .In the broader scheme of things, diatoms help us air breathers by photosynthesizing and producing oxygen. They further contribute to the ecosystem by being fed upon by such microscopic creatures as the horn-shaped Stentor, which themselves are fed upon by larger organisms, and so on up the food chain.

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WINTER ANNUALS GREENING THE GROUND
Winter annuals are plants that germinate in autumn, live through the winter, and produce seed and die the following season. Up North and where there's generous rainfall you can find winter annuals at this time of year -- especially weeds such as Chickweed, Henbit and Shepherd's-purse -- but it seems that here at the arid edge of the Chihuahua Desert winter annuals seem to occur in much greater numbers and diversity. They're not only weed species but also plants highly adapted to our often harsh habitats, such as the thin, droughty soil atop limestone, and in the cobble fields along the Dry Frio River. In many places, despite this being early winter, the ground is green and springy looking, as shown at https://www.backyardnature.net/n/12/121223wa.jpg.

There are reasons why being a winter annual in our edge-of-desert environment would be a good living strategy for a plant. One explanation is suggested by the fact that no annual plants occur in the polar regions or wet tropics. In both of those environments, intense competition for suitable growing sites favors perennial plants, who live by the motto "Once you've got it, hang onto it for more than one season." However, in our edge-of-desert environment, perennials are widely spaced because they need to send roots through a large soil area in order to attain water during drier years. Much in contrast, during a brief rainy season or a not-too-cold winter such as we have here, herbs can live their entire lives between the widely-spaced perennials.

A general rule in North America is that the more arid the habitat, the greater the proportion of annual species to perennial ones, and a lot of those annuals will be winter annuals.

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LETTUCE
Especially on cold mornings when sunlight pours in from the east with its special edge-of-desert intensity and sharpness, the lettuce is so pleasing to look at, its frilly, tender leaves glowing with yellow-greenness and burgundy shades, as shown at https://www.backyardnature.net/n/12/121223lt.jpg.

Our first freeze of the season sneaked up on me so I hadn't properly covered the lettuce bed the night of the freeze. That morning the lettuce was hoary with frost and I thought that by the afternoon it'd be brown and soggy, but the freeze didn't seem to hurt it at all. In fact, studies show that while many cultivated plants such as potato, corn and tobacco can't survive freezes, leaves of plants such as cabbage, lettuce, and spinach can develop tolerance to below-freezing temperatures in response to recent low but above-freezing temperatures. We'd had some cold nights prior to the first freeze, so that must have induced freeze tolerance for my lettuce on the freezing night. One way that gradually lowering temperatures over a period of days can produce freeze tolerance is to cause plants to lower their water content and develop thicker leaves.

If you've seen the yellow, Dandelion-like flowers and fruits of lettuce that's gone to seed, you probably recognized that lettuce is a member of the Composite or Sunflower Family. Many kinds of lettuce exist, all with the binomial LACTUCA SATIVA. Traditionally four taxonomic varieties of Lactuca sativa have been recognized: capitata, with its head lettuce; longifolia, with its romaine lettuce; crispa, with its curled-leaf lettuce, and; asparagina, with its thick, edible stems.

Our picture shows a curled lettuce of the variety crispa. It's further distinguished as a "red leaf lettuce," and there are several different cultivars of red leaf lettuce on the market. You might enjoy looking at the numerous lettuce cultivars illustrated on Dave's Garden Lettuce Page at http://davesgarden.com/guides/pf/finder/index.php?sname=Lettuce.

Lettuce's history of cultivation has been nicely documented. Egyptians first domesticated it not for its edible leaves but for oil from its seeds, then later selectively bred it for its leaves. There's evidence of its cultivation in Egypt as early as 2680 BC. From Egypt lettuce was passed to ancient Greece and then to the Romans, who already by 50 AD were able to describe several lettuce varieties. By the 1500s Europeans were recognized the basic leaf-lettuce types -- head, loose-leaf and romaine. Columbus himself introduced lettuce in the Americas. By the late 1800s between 65 and 140 distinct kinds of lettuce were recognized.

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FEATURED ESSAYS FROM THE PAST:

"Cold Days at Peace," from the January 5, 2003 Newsletter, at https://www.backyardnature.net/n/p/030105.htm

"Cracking Pecans," from the January 11, 2004 Newsletter, at https://www.backyardnature.net/n/p/040111.htm

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Best wishes to all Newsletter readers,

Jim

Visit Jim's backyard nature site at https://www.backyardnature.net