Weaving Terms

Day 110: Several of my loyal and faithful readers have remarked to me recently that they feel like they're reading a foreign language when I'm talking about weaving. I find it odd that this didn't surface as I rambled on about fungi, slime molds, lichens or some rare plant I'd stumbled across in the backcountry, but there ya go: no accounting for how a writer's efforts are received by their audience, and I'm just happy to know that my work is being read. All things considered (not the least of which might be the paucity of bloggable material during isolation), I have decided that over the next several days, I will present a few weaving terms with explanatory photographs which hopefully will help folks follow along.

Let's start at the very beginning (a very good place to start, do-re-mi). If you look at a piece of woven cloth, you will see that it is comprised of threads running both vertically and horizontally. Turn it so that the selvedges (edges) are on your left and right. The threads which run lengthwise are the warp threads (left), and those running across are the weft (a patterned weft is shown top right). The warp threads are held taut by the loom, tied down on either end. Today, we'll just concern ourselves with the weft (the "active" thread controlled by the weaver's shuttle) and how it passes through the warp.

In order to make cloth, some sort of over-under pattern must be established. The simplest is tabby weave: one thread up, one down across the entire width of the cloth. The first looms were established to make this easier by raising or lowering every other thread simultaneously rather than picking them up one at a time by hand. On a floor loom, this is done by depressing a treadle which in turn operates a mechanical device in which that half of the threads are held. This device (harness and heddles) will be explained in a future post. When the alternate threads are raised or lowered and the developing cloth is viewed from the side, it will be seen that there is a triangular gap between the two layers of "up" and "down" threads. This is called the shed (lower right photo). Doesn't it remind you of a woodshed? See how the "roof" slopes down toward the front? The shuttle carrying the weaving thread (weft) is passed through the shed, and the "throw" is beaten into place. Then the weaver depresses a different treadle and the opposite threads are raised or lowered, forming the alternate shed. The shuttle goes through again, the thread is beaten into place, and the first two rows of cloth have been formed, interlaced over-and-under like weaving a basket. In the top right photo, the lavender threads are woven in that over-and-under (tabby) pattern. Indeed, much of the cloth on the market today as both yardage and finished goods is woven either as tabby or as twill (a sequence of four threads progressing on the diagonal), but as you can see in the dark blue pattern above, there are many other possibilities to be made by simply raising or lowering different threads. That's where heddles come in, and for that, you'll have to tune in tomorrow.

Ramalina Farinacea, Sorediate Margins

Day 76: Lichen terminology can be very confusing even for botanists because certain structures have no counterpart in the physiology of vascular plants. My readers will have heard me use the term "soredia/soredium" for a specific type of vegetative propagule generated by some lichens, and they may also recall having read the word "soralia." Soralia are where soredia are produced. They manifest as small patches where the lichen cortex ("skin") has cracked or broken down. The emerging soredia often have a granular appearance and lack any cortex; soredia are one of the parent lichen's means of reproducing. In the inset, you can see the soralia/soredia along the margins of this fine specimen of Ramalina farinacea from Ohop Valley. Many lichens have more than one reproductive strategy to ensure their survival as species. Some are capable of reproducing both sexually and asexually. On the whole, lichens are atonishingly successful in the natural scheme. They were here long before humankind, and unless we pollute them out of existence, they will endure long after evidence of our brief passage has faded from the surface of the Earth.

Weaving Mechanics

Day 76: I realize some of you are having trouble following the specialized terminology inherent with weaving, so I've put together a handy-dandy guide to the mechanics of a loom and how the warp is slung. I realize now that I should have lettered it from right to left because that's the direction warping proceeds, but I think we can work with this.

As you saw in yesterday's post, the first part of the process is stretching the warp. Here, we are picking up the method with the warp wound onto the warp beam (J). This consists of a large roller on which is mounted a canvas "apron." The apron serves to keep the warp threads from stacking up on themselves as the roller is turned. As the warp is wound beyond the apron, posterboard or some other separator is used to cushion the threads. (H) shows the warp on the roller.

The warp comes from the roller and may pass through a raddle (I) mounted on the back beam. This optional device divides the warp threads into bundles and helps keep the tension even. A loose warp thread can cause all sorts of problems in the cloth! From the raddle, the warp threads come forward horizontally (G) and each passes through a heddle in a specific order. This is what determines the pattern of the weave. The heddles are held in harnesses (D), frames which are raised in sequence by means of treadles. At (E), the loose warp is hanging at the front of the heddles, ready for the next step; at (C), the warp is through the heddles and reed (A).

Now the warp threads must pass through the reed (A) which is held in the beater bar (B). The beater bar is the portion of the loom which beats the weft threads into place. It is operated by the weaver's free hand, the other being occupied with the shuttle. From the reed, the warp is then brought over the breast beam (not shown) and tied to the front apron. As weaving progresses, the finished fabric is wound onto the cloth beam (F), a roller similar to that at the back of the loom.

There are other methods of sleying a loom (the term used for this whole procedure), and will vary according to the weaver's preference and the type of loom being employed. Mine is a four-foot, four-harness rising-shed loom, i.e., the treadles cause the harnesses to rise rather than sink. I also have a three-foot, four-harness table loom which is operated with jacks (hand levers) rather than treadles. Since my shoulder reconstruction, I have found the jack loom difficult to use. That said, the rhythm of weaving is almost meditative, and once I'm in the swing of passing the shuttle back and forth, I can relax into it, knowing that the hard work of threading is behind me.

Dichotomously Branched Rhizines

Day 1 of YEAR EIGHT! I'm going to start you off with a couple of those big "science words" I throw around so freely because it's crucial to know what to look for if you're trying to identify this particular common lichen. Parmelia hygrophila grows on tree bark and is grouped with others as "shield lichens," meaning that they form a mass which adheres closely to the substrate (i.e., the bark, in this case). We refer to this as being "tightly appressed," but that's a feature shared with a lot of other lichens. The words I'd like to introduce are "rhizine" and "dichotomous." "Rhizine" refers to the root-like structures on the back side of the thallus (body). Sometimes these structures are so fine that you need a microscope to see them. At the very least, you need a hand lens to tell how those of the Parmelias branch. Enter "dichotomously," i.e., they form two-pronged forks ("di-" means "two").

Looking at these under a 20x stereo microscope, it's easier to identify individual rhizines if you view a piece of the thallus from the top and observe where they stick out along the sides. Viewed from the bottom, they just look like a mass of tangled threads. Note the inset in the upper left. See how some of the threads have split ends? That's "dichotomous branching." Parmelia hygrophila exhibits dichotomous branching, as opposed to its look-alikes P. saxatilis (unbranched) and P. sulcata, which has squarrulose ("bottlebrush") rhizines. We'll save "squarrulose" for another day.

Making A Determination

Day 143: It's taken me three days to make a final determination as to the identity of this unusual Cladonia based on field characteristics alone. I lack the reagents which would give me conclusive results for this particular species, but given that it does not conform to all the physical characteristics any other option, I have placed it as Cladonia ecmocyna, which in any event is highly variable. Some squamules are visible on the podetia; podetia are pointed and frequently browned; the apothecia are infrequent and brown; narrow cups do form at some podetial tips.

I believe I may have mentioned this before, but I think one of the things which attracted me to the study of lichens is the exotic vocabulary which accompanies them. Words like "pruina" or "pseudocyphellae" don't crop up in just any conversation, but if I'm given the chance, you'll hear them fall from my tongue as smoothly as if they were poetry. In fact, if you were following along behind me secretly on a walk in the woods, you'd hear me muttering them to myself as I survey the surrounding lichenscape, describing it aloud to no one in particular. If you tailed me long enough, though, you might hear the one botanizing phrase I most enjoy using, the precise and highly technical expression I voiced when I encountered the (presumed) Cladonia ecmocyna in Longmire Campground. Nothing excites me more than having a chance to say, "What the hell is THAT?"

Pale Male

Day 233: Somebody bleached one of my Goldfinches! I'm kidding, of course, but although there is some degree of variation as these birds pass from drab winter colours to their yellow summer finery, I have never seen one quite as white as this guy.

Scholars will disagree on whether this variation should be referred to as "partially leucistic" or "dilute." David Allen Sibley says, "The term leucistic has a confused history. In the introductions of the Sibley Guides I said the term leucistic is synonymous with dilute plumage. That usage was fairly common among birders at the time, and I was unaware that it contradicted several scholarly publications (e.g. Buckley 1982, van Grouw 2006) which define leucistic as the total lack of melanin from some or all feathers (what I called partial albino in the guides). It does make sense to distinguish birds that are unable to deposit melanin (my partial albino, their leucistic) from birds that are able to deposit melanin but only in low concentrations (my leucistic, their dilute)...I’ve used the term leucistic (not partial albino) for birds which cannot deposit melanin, which helps to distinguish these birds from the narrowly-defined true albino, and allows use of the term 'partial albino' as a general category for any bird showing any form of reduced melanin."

If you find this confusing, don't fret. It is a good example of how plastic the sciences are. While good scientists like Sibley try to stay abreast of research, it sometimes gallops ahead so rapidly that it's hard to keep up. For now, it seems safer to refer to my washed-out Goldfinch as a "pale male."

Bellidiflora Up Close And Personal

Day 202: I recently purchased a snap-on macro filter thinking that I'd be able to get more detail for the field-guide style shots I present to my readers. I was only half right. While shooting macros does bring you "up close and personal" with your subject, the "field guide" aspect is lessened due to the diminished depth of field which excludes any habitat features one might use in making a solid identification. A good zoom keeps that frame of reference by allowing foreground and background detail when desired. Personally, I find out-of-focus foreground material distracting (the moss in this shot, for example). In macro photography, it is difficult to avoid when the camera is placed at a side-on angle. That said, a photo like this one could be useful in a classroom situation where the instructor wants to define terms: apothecia, squamules, podetia, primary and secondary thalli. Add a couple of arrows, and you have a PowerPoint slide for Lichens 101.

Cladonia bellidiflora would make a good poster child for lichen-speak. The bright red apothecia appear at the tips of podetia thick with ragged squamules. Even without arrows, you can recognize those parts.