The Ulmaceae and Moraceae constitute two closely related families with representatives in many parts of the world. Although probably best known for their namesake trees, fhe true elms and mulberries, the common names for both families are somewhat misleading because each one also contains a fairly diverse assemblage of plants (hat are not often associated with either of these genera.
The Ulmaceae is a worldwide family of 15 genera and upwards to about 200 species. The family is composed mostly of temperate tree species and encompasses four genera in the I nited States, all of which are represented in Florida. These genera include Ulmus t or the true elms; Celt is. which is made up of the hack berries or sugar-berries: Planer a, a monotypic genus that occurs only in the southeastern United States; and Trema, one of the family's few tropical genera and the only U.S, member of the family confined strictly to southern Florida,
Fossil data indicate that the Ulmaceae had ancient origins and were once widespread in distribution. The remains of fossilized pollen offers strong evidence that the elms were extanl at least as far back as Miocene times, or about 25 million ago. In addition, remarkably intact fossilized elm leaves have been found by researchers excavating an ancient Oregon creekbed. According to researchers Giannasi and Niklas in their 1977 article for Science magazine, these antediluvian leaves still retained their greenish color and showed little chemical difference from those species growing in North America today.
R. II Kichens, in his book Elm* suggests that the close relationship between several of the Old and New World species probably also indicates that many members of the family may have existed even prior to the continental drift that separated the Americas from the Eurasian mainland. The Wye he elm common in Europe and the British Isles, for example, is included in the same taxonomic assemblage as the slippery elm of eastern North America; and Ulmus laevis, a species of central and eastern Furope, is closely associated with our own American elm. All of this suggests a common ancestry that would be difficult to explain if these species had not once occupied the same land mass.
Today, the members of the genus Ulmus are some of (he best known of American trees.. Although often thought of as New England shade trees, several species also occur in the southeast.
Florida has four true elms, the largest of which is Ulmus americana. The American elm, as this tree is commonly known, is an associate of flood plain forests and moist woodlands across northern Florida and into the central peninsula. It is one of the last trees u> shed its foliage in winter and one of the first to put out flowers in spring. Even
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