THE ELM, PLANER AND HACKBERRY 153 



tribution of the elms, but we are ignorant of the details during that 

 dramatic period of earth history. Eight different species of elm 

 have been found in Pleistocene deposits. Most of these represent 

 species that still exist, but supposed extinct forms have been de- 

 scribed from England and Maryland. The common European 

 elm, Ulmus campestris, has been found fossil in France, Italy and 

 Crimea. Our common American elm, Ulmus amsricana, occurs in 

 the Pleistocene in Maryland and in interglacial deposits of Ontario. 

 Our southern winged elm or wahoo, Ulmus alata, has been found 

 fossil in North Carolina, Alabama and Kentucky; and the northern 

 cork or rock elm, Ulmus racemosa, is present in the Pleistocene 

 river terraces near Morgantown, West Virginia, and in the inter- 

 glacial beds of the Don Valley near Toronto. 



THE PLANER TREE 



The planer tree or water elm belongs to a genus known as Planera 

 and named in honor of Johann Jacob Planer, a German physician 

 and botanist of the eighteenth century. Specifically the single 

 living species is known as aquatica in allusion to its most common 

 habitat in wet swamps. It is a small tree, with a short trunk rarely 

 if ever reaching 2 feet in diameter, with slender spreading branches 

 forming a low broad head, and light soft wood of no particular 

 value. It IS found at the present time from North Carolina south- 

 ward to and along the Gulf Coast as far as the Trinity River in 

 Texas, and reaches its largest size in the swamps of Louisiana and 

 southern Arkansas. It is the sole living representative of the 

 genus and it is probably becoming gradually more restricted in 

 range since it formerly reached farther northward, being found 

 in Maryland and Kentucky during the late Pleistocene. Its 

 leaves are distinguishable with difficulty from those of some of the 

 ehns, and considerable uncertainty pertains to the determination 

 of some of the earlier species. 



Four species of these trees have been recorded from the Upper 

 Cretaceous, and all of these come from the Western Hemisphere 

 where they are found in Greenland, and in what is now the Atlantic 

 Coastal Plain from Marthas Vineyard, New Jersey and North 



