Ulmus (Ulmaceae)

Ulmus americana
U Conn Plant Database

Ulmus americana

Ulmus americana

Deciduous tree, to over 75 ft (23 m), arching, or spreading branches. Alternate, simple leaves, 7.5-15 cm, ovate-oblong, unequal at base, doubly serrate. American Elm has been decimated by the usually fatal Dutch Elm Disease. Ulmus contains about 45 species native to Asia [11], Europe and the Mediterranean [6], South and Central America [7] and North America [7].

Pollen light micrograph:
Oblate, 35-40 µm., stephanoporate with 5 (4) oval pores, rugulate. Easily recognized by its unique "brain-like" sculpture pattern and pentagonal shape.

Pollen scanning electron micrograph (SEM)
Sculpture pattern complex.

Production and Dispersal:
Typically present in small percentages, but abundant production. Characteristic of the Eastern Deciduous forest of North America.

Moderately well preserved.

Fossil Occurrence:
A characteristic species of the New World and Old World Tertiary, possibly present in the the Maastrichtian Hell Creek Flora. The pollen of Cretaceous Ulmoideipites krempii is similar, but typically with 3 (4) pores and arci. Ulmus pollen is difficult (impossible) to distinguish from that of Zelkova. Pollen and macrofossils of both genera are present from at least the Eocene of North America.
Elm is the key species of the Atlantic period (Mid Holocene 8000 - 5000 yr B.P.) of the European "Blytt Syrnander" sequence.

    Sticklen, M.B., M.G. Bolyard, R.K. Hajela and L.C. Duchesne. 1991.
    Molecular and cellular aspects of Dutch elm disease. Phytoprotection 72(1):1-13

    Gil, L. and M.E. Garcia-Nieto Rivero. 1990.
    [Paleobotanic and history of elms in the Iberian peninsula] Paleobotanica e historia de los olmos de la peninsula iberica. Chap. 2, pp. 29-65 in Los Olmos y la Graphiosis en Espana (L. Gil, ed.). ICONA

    Lappalainen, V. 1965
    The Ulmus decline in postglacial pollen diagrams from southeastern Finland. The Geological Society Of America Special Paper 84


Owen K. Davis 06/00