Some information that is helpful before you read (or in addition to reading) this article is contained here in the overview article http://www.woodbarter.com/threads/wood-anatomy-an-introduction.18349/
PARENCHYMA
If you have a "mystery wood" that you want to ID, there are a number of things you can do including sending a sample to the USDA and waiting months for a reply. A better method is to take good pics and post them here on Wood Barter asking if anyone can ID it for you. That often works, but not always. This article is one of a pair of articles that show how, with a pretty modest amount of effort, you might well be able do it yourself.
The two articles are about how to use a simple 10X loupe and some fine-grit sandpaper to expose wood anatomy to an extent that allows for some pretty nifty analysis of the wood. This article is about parenchyma and the other is about growth rings. Parenchyma is less familiar to woodworkers than at least the rudiments of growth rings, but most folks are pretty startled when they realize the details that are available with so little effort to make both growth rings and parenchyma visible and useful in wood ID.
The growth rings article is at: http://www.woodbarter.com/threads/wood-anatomy-growth-rings.18348/
Parenchyma cells are wood tissue that is used by a tree to store and distribute carbohydrates (tree food). Not all woods have clearly distinguishable parenchyma but most hardwoods do and with a little effort, they can be invaluable in identifying woods. You'll find it really surprising, I think, to see how many different constructs these little devils can take and the extent to which they are useful in identifying wood species, and I emphasize again that it is not very hard to get them to show up for your viewing pleasure.
Some parenchyma groups are attached to pores, some are not. These two different categories have technical names but that's getting too far down in the details for this article. There are numerous technical terms used with parenchyma, and they mostly make very good sense and are pretty easy to remember, as I have attempted to show with some of them in this article.
I'm not going to replicate the full parenchyma discussion that is on my site, because it's a bit too long (and there are WAY too many pics for this light-weight discussion), but here I will show how radically different the parenchyma can be for different woods and how easy it is to use in wood identification. Again, you DO have to have a 10X loupe and a willingness to do a bit of sanding, but that's all. I sand wood for my pics down to 1200 grit but most distinctions can be made if you sand down to 400 grit (progressively going through several grits so that when you end up you don't have any scratches from the original cutting or from the subsequent grits). I suggest 100 grit, 220 grit, 320 grit, then 400 grit. I use a ROS but a belt sander works just as well to 400 grit.
Parenchyma cells run in several different orientations and wood scientists use transverse (end grain), radial (quartersawn), and tangential (flat cut) surfaces to evaluate them, but the analysis I use, and what I'm describing in this article, only uses the end grain, so all you need to do is get an end grain section at least about 1/2" by 1" and sand it down and look at it through the 10X loupe. The other orientations generally require better magnification and better preparation of the wood, which is why I don't use them.
More often than not, parenchyma cell formations are not limited to a single type and it can be informative that two or more particular types are present in a sample. In this short article, I am focusing on some of the major types individually and with only limited discussion of the combinations. The full article goes into things in much more detail and is more rigorously organized than this light-weight article.
With some knowledge of the types of parenchyma, which this article will get you started on, you can look on my parenchyma pages, which are organized by type of parenchyma, to hone in on the wood you are tying to identify.
SO ... get out the sandpaper and the loupe and here are some examples of what you'll see:
I start with "lozenge shaped aliform" parenchyma simply because this particular sample gave me the best end grain shot of all the 2000+ I've taken and I love to show it off:
kempas, showing lozenge-shaped aliform parenchyma
"Aliform" means "wing shaped" and if you've ever had a sore throat, you'll know what "lozenge shaped" means. Aliform parenchyma groups come in two subtypes, "lozenge shaped" and "wing shaped". The piece of kempas shown directly above has some very clearly defined lozenge shaped groups.
Since "aliform" means "wing-shaped", it seems redundant to say "wing shaped aliform" parenchyma, but it is simply to distinguish that type from the lozenge shaped. Here are some samples of the "wing shaped" type of aliform groups.
limba, padauk, and padauk again, all showing wing-shaped aliform parenchyma
These wing shaped aliform parenchyma groups look a bit like a bunch of WWII fighter planes headed straight for you, with the wood pore being the body of the plane. In the 3rd pic of this set, the "wings" extend quite far and often they go from one pore to the next, which is actually yet another type of parenchyma grouping known as "confluent" (which literally means "flowing together or merging").
Here are some samples of confluent parenchyma:
desert ironwood, sucupira, and wenge, all showing confluent parenchyma
In the wenge, the confluent groups are often (as they are in the sample above) among the strongest you will see in any wood. There is another type of group which has continuous bands of confluent parenchyma all the way around the tree and that type is called ... wait for it ... "banded" parenchyma.
Before moving on to banded parenchyma, here's an example of using parenchyma to distinguish between closely related species
Oregon ash (Fraxinus oregona) and velvet ash (Fraxinus velutina) showing subtle, but clear, differences in confluent parenchyma distribution.
In the Oregon ash there are a few confluent groups right at the end of the latewood in each growth ring whereas in the velvet ash there are numerous confluent groups starting in the middle of the growth ring and getting thicker out towards the end of the latewood.
Now, getting back to banded parenchyma, in the example of confluent parenchyma above, you could see that the lines of parenchyma were broken up. Here's an example of where they are continuous:
mockernut hickory showing banded parenchyma
All of the thin lines running around the tree (the horizontal lines in this pic) parallel to the growth rings but more numerous than the growth rings are banded parenchyma. As you can see, the pores themselves have whitish vessels surrounding them, which is yet another type of parenchyma known as "vasicentric".
"vasi" means "vessel" and one of the meanings of "centric" is "concentrated around", so not surprisingly, "vasicentric" means "concentrated around the vessel" and the particular vessel in this case is the pore. Lozenge shaped aliform parenchyma groups seen earlier are a type of vasicentric parenchyma, but because they are an identifiable sub-type, they have their own name.
tiama, sucupira, and timbo, all showing vasicentric parenchyma
Vasicentric groups can be so small as to be pretty much invisible at the level of a 10X loupe, which would be even smaller than what is shown in this sample of tiama, or they can be noticeable but not huge, as in this sample of sucupira, or they can be quite large as in this sample of timbo.
One last type I'll mention in this brief article is "marginal" parenchyma, so called because it occurs at the margin between the latewood of one growth ring and the earlywood of the next. In some woods, the marginal parenchyma is the only indication that there IS a growth ring.
Honduras mahogany showing marginal parenchyma (and a thin line of vasicentric parenchyma around each pore)
This sample of Honduras mahogany shows the strong, continuous line of marginal parenchyma that is typical of the Swietenia mahogany species. It can sometimes be used to distinguish Swietenia mahoganies from the Khaya (African mahogany) species because the marginal parenchyma in the African species is rarely so strong and sharply defined and almost never continuous.
So I hope this has whetted your appetite to try some of this for yourself. Most of the samples in this brief article are exotics. My site has extensive pics of the parenchyma for most domestic woods but the growth ring characteristics tend to be more informative for domestics, and that is the subject of the other of these two brief articles.
PARENCHYMA
If you have a "mystery wood" that you want to ID, there are a number of things you can do including sending a sample to the USDA and waiting months for a reply. A better method is to take good pics and post them here on Wood Barter asking if anyone can ID it for you. That often works, but not always. This article is one of a pair of articles that show how, with a pretty modest amount of effort, you might well be able do it yourself.
The two articles are about how to use a simple 10X loupe and some fine-grit sandpaper to expose wood anatomy to an extent that allows for some pretty nifty analysis of the wood. This article is about parenchyma and the other is about growth rings. Parenchyma is less familiar to woodworkers than at least the rudiments of growth rings, but most folks are pretty startled when they realize the details that are available with so little effort to make both growth rings and parenchyma visible and useful in wood ID.
The growth rings article is at: http://www.woodbarter.com/threads/wood-anatomy-growth-rings.18348/
Parenchyma cells are wood tissue that is used by a tree to store and distribute carbohydrates (tree food). Not all woods have clearly distinguishable parenchyma but most hardwoods do and with a little effort, they can be invaluable in identifying woods. You'll find it really surprising, I think, to see how many different constructs these little devils can take and the extent to which they are useful in identifying wood species, and I emphasize again that it is not very hard to get them to show up for your viewing pleasure.
Some parenchyma groups are attached to pores, some are not. These two different categories have technical names but that's getting too far down in the details for this article. There are numerous technical terms used with parenchyma, and they mostly make very good sense and are pretty easy to remember, as I have attempted to show with some of them in this article.
I'm not going to replicate the full parenchyma discussion that is on my site, because it's a bit too long (and there are WAY too many pics for this light-weight discussion), but here I will show how radically different the parenchyma can be for different woods and how easy it is to use in wood identification. Again, you DO have to have a 10X loupe and a willingness to do a bit of sanding, but that's all. I sand wood for my pics down to 1200 grit but most distinctions can be made if you sand down to 400 grit (progressively going through several grits so that when you end up you don't have any scratches from the original cutting or from the subsequent grits). I suggest 100 grit, 220 grit, 320 grit, then 400 grit. I use a ROS but a belt sander works just as well to 400 grit.
Parenchyma cells run in several different orientations and wood scientists use transverse (end grain), radial (quartersawn), and tangential (flat cut) surfaces to evaluate them, but the analysis I use, and what I'm describing in this article, only uses the end grain, so all you need to do is get an end grain section at least about 1/2" by 1" and sand it down and look at it through the 10X loupe. The other orientations generally require better magnification and better preparation of the wood, which is why I don't use them.
More often than not, parenchyma cell formations are not limited to a single type and it can be informative that two or more particular types are present in a sample. In this short article, I am focusing on some of the major types individually and with only limited discussion of the combinations. The full article goes into things in much more detail and is more rigorously organized than this light-weight article.
With some knowledge of the types of parenchyma, which this article will get you started on, you can look on my parenchyma pages, which are organized by type of parenchyma, to hone in on the wood you are tying to identify.
SO ... get out the sandpaper and the loupe and here are some examples of what you'll see:
EACH OF THE PICS SHOWN ON THIS PAGE IS OF A
1/4" X 1/4" END GRAIN CROSS SECTION SHOWN HERE AT 12X
I start with "lozenge shaped aliform" parenchyma simply because this particular sample gave me the best end grain shot of all the 2000+ I've taken and I love to show it off:
kempas, showing lozenge-shaped aliform parenchyma
"Aliform" means "wing shaped" and if you've ever had a sore throat, you'll know what "lozenge shaped" means. Aliform parenchyma groups come in two subtypes, "lozenge shaped" and "wing shaped". The piece of kempas shown directly above has some very clearly defined lozenge shaped groups.
Since "aliform" means "wing-shaped", it seems redundant to say "wing shaped aliform" parenchyma, but it is simply to distinguish that type from the lozenge shaped. Here are some samples of the "wing shaped" type of aliform groups.
limba, padauk, and padauk again, all showing wing-shaped aliform parenchyma
These wing shaped aliform parenchyma groups look a bit like a bunch of WWII fighter planes headed straight for you, with the wood pore being the body of the plane. In the 3rd pic of this set, the "wings" extend quite far and often they go from one pore to the next, which is actually yet another type of parenchyma grouping known as "confluent" (which literally means "flowing together or merging").
Here are some samples of confluent parenchyma:
desert ironwood, sucupira, and wenge, all showing confluent parenchyma
In the wenge, the confluent groups are often (as they are in the sample above) among the strongest you will see in any wood. There is another type of group which has continuous bands of confluent parenchyma all the way around the tree and that type is called ... wait for it ... "banded" parenchyma.
Before moving on to banded parenchyma, here's an example of using parenchyma to distinguish between closely related species
Oregon ash (Fraxinus oregona) and velvet ash (Fraxinus velutina) showing subtle, but clear, differences in confluent parenchyma distribution.
In the Oregon ash there are a few confluent groups right at the end of the latewood in each growth ring whereas in the velvet ash there are numerous confluent groups starting in the middle of the growth ring and getting thicker out towards the end of the latewood.
Now, getting back to banded parenchyma, in the example of confluent parenchyma above, you could see that the lines of parenchyma were broken up. Here's an example of where they are continuous:
mockernut hickory showing banded parenchyma
All of the thin lines running around the tree (the horizontal lines in this pic) parallel to the growth rings but more numerous than the growth rings are banded parenchyma. As you can see, the pores themselves have whitish vessels surrounding them, which is yet another type of parenchyma known as "vasicentric".
"vasi" means "vessel" and one of the meanings of "centric" is "concentrated around", so not surprisingly, "vasicentric" means "concentrated around the vessel" and the particular vessel in this case is the pore. Lozenge shaped aliform parenchyma groups seen earlier are a type of vasicentric parenchyma, but because they are an identifiable sub-type, they have their own name.
tiama, sucupira, and timbo, all showing vasicentric parenchyma
Vasicentric groups can be so small as to be pretty much invisible at the level of a 10X loupe, which would be even smaller than what is shown in this sample of tiama, or they can be noticeable but not huge, as in this sample of sucupira, or they can be quite large as in this sample of timbo.
One last type I'll mention in this brief article is "marginal" parenchyma, so called because it occurs at the margin between the latewood of one growth ring and the earlywood of the next. In some woods, the marginal parenchyma is the only indication that there IS a growth ring.
Honduras mahogany showing marginal parenchyma (and a thin line of vasicentric parenchyma around each pore)
This sample of Honduras mahogany shows the strong, continuous line of marginal parenchyma that is typical of the Swietenia mahogany species. It can sometimes be used to distinguish Swietenia mahoganies from the Khaya (African mahogany) species because the marginal parenchyma in the African species is rarely so strong and sharply defined and almost never continuous.
So I hope this has whetted your appetite to try some of this for yourself. Most of the samples in this brief article are exotics. My site has extensive pics of the parenchyma for most domestic woods but the growth ring characteristics tend to be more informative for domestics, and that is the subject of the other of these two brief articles.
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