Mark, on that unknown, it has been dead for a long time. There were about 4 pieces firewood lengths lying on the ground for a long, long time. They were easy to pick up and toss into the truck, so any readily available wood does not go to waste around me. When I cut one later that day, I was surprised to see it wasn't Mesquite. It could be African American Sumac. It has some of the color, but I don't see any tiny inclusions like those in the pieces I got years ago...............
Creosote Bush (Greasewood, locally) and Ocotillo are a piece of cake, but the sizes possibly won't make the standards you need for samples.
The Brittle Brush I have plenty growing on my property, but the stuff is pretty small and the 1/2" OD stems are very fragile after drying out. They are weeds, same as Berlandier wolfberry (Lycium belandieri), which also is growing here.
I actually had an Ocotillo die this year. The stems/sticks are about 1+ inch in diameter. I'll see how big they are at the root.
You need any Devil's claw? That's as brittle as the Brittle Brush.
How about a couple Saguaro ribs? Some are huge, about 4-5" but start tapering pretty quickly. .
One of these days I'll hit you up for postage on a box, and then send you this stash. ............. Jerry (in Tucson)
I am not familiar with many of them, just read they that are associates of the yellow palo verde and was shooting in the dark. Laminates are a pain, and I hinder you enough. So packing a bunch of brittle items probably not worth it, unless you are sending some of the cacti group. I have 'chain-fruit and staghorn cholla' and hope to get some 'saguaro'
sewaro cactus, Carnegiea gigantea some day. Actually, just happy to add to the collection for the most part. Here is a south american relative.