Trees of the family Ulmaceae, genus Ulmus. There are many different Species. You probably have a pretty good idea of what an Elm looks like. That picture of a generic tree you have in your mind... no, not the pine; the big angiosperm standing off by itself. Yep, that's an elm.
The leaves are the traditional leaf (deciduous, leaf shaped, toothed edges). The bark, is again traditional (usually brownish-gray, and bumpy). Height, traditional (80-120 FT.). A tree's tree.
And being a tree, it gets cut down and chopped up. Elm wood is tough and hard, and doesn't spilt easily. Ulmus thomasii and Ulmus americana are a little hard to work easily, but are strong. Ulmus rubra is more pleasant to work with, has the advantage of being both shock and wear resistant, and it steam-bends nicely.
In the early 1900s, Dutch elm disease appeared in Europe, probably having come from Asia. By the 1930s it had made it to America, and today has made it pretty much everywhere there are elms. It has killed untold millions of elm trees, wiping out entire forests. An infected tree will start wilting, it leaves turning yellow and dying. Within a few years, the tree will die. It is caused by the fungus Ophiostoma ulmi (sometimes called Ceratocystis ulmi), which is spread by the elm bark beetle. Species of elm trees from Asia, such as the Chinese elm and Siberian elm, are much more resistant to Dutch elm disease than are European and American species.
Other diseases that infect elm trees are Elm yellows (AKA elm phloem necrosis), and Bacterial leaf scorch.
And, for your viewing pleasure, here are some of the more common elms, and their Latin names. Enjoy!
American Elm, White Elm, Florida Elm, Swamp Elm, Water Elm; Ulmus americana L.
Basket Elm, Cedar Elm, Southern Rock Elm; Ulmus crassifolia
Camperdown Elm, Umbrella Elm, Weeping Elm; Ulmus glabra camperdownii.
Chinese Elm, Hokkaido Elm, Lacebark Elm; Ulmus parvifolia
Cork Elm, Hickory Elm; Ulmus Thomasii
Dutch Elm, Cork Bark Elm; Ulmus hollandica (This is often written Ulmus x hollandica)
English Elm; Ulmus procera or Ulmus campestris
European White Elm; Ulmus laevis
Japanese elm; Ulmus japonica
Nave Elm; Ulmus campestris or Ulmus procera
Red Elm; Ulmus campestris, Ulmus crassifolia, Ulmus procera, or Ulmus rubra
Rock Elm; Ulmus alata, Ulmus crassifolia, or Ulmus thomasii
Scotch Elm, Scots Elm, Wych Elm, Irish Leamhan, Mountain Elm; Ulmus glabra Huds.
Siberian Elm; Ulmus pumila L.
Slippery Elm, Gray Elm, Soft Elm, Moose Elm; Ulmus rubra Muehl.
Smooth-leaved Elm; Ulmus minor
Winged Elm, Hard Elm; Ulmus alata.
Closely related trees sometimes called elms:
Bastard Elm, False Elm (Common Hackberry, American Hackberry); Ulmaceae Celtis occidentalis
Japanese Zelkova; Ulmaceae Zelkova serrata