94 THE MICHIGAN BOTANIST Vol. 41 THE BIG TREES OF MICHIGAN 29. Betula papyrifera Marshall var. cordifolia (Regel) Fern. Mountain Paper Birch Kenneth M. Hiser & Elwood B. Ehrle Department of Biological Sciences Western Michigan University Kalamazoo, MI 49008 The largest known Mountain Paper Birch tree in Michigan, as well as in the United States, is located near the Sleeping Bear Dunes in Leelenau County, in the northwest portion of the lower peninsula. Voss (1985) does not recognize this element, nor do Barnes & Wagner (1981). It is accorded specific rank in Flora of North America (as Betula cordifolia Regel); clearly, there is some lack of una- nimity among taxonomists. Description of the Species: The Mountain Paper Birch is a member of the Birch family, Betulaceae. In Michigan, the family is represented by a number of large shrub and tree genera. Members of the Birch family are typically monoe- cious, producing catkins of unisexual, apetalous flowers, both kinds of catkins on the same tree. These appear before leaves are mature in spring, and are wind- pollinated. Voss (1985) distinguishes between two tribes within the family, Be- tuleae and Coryleae. The two tribes are most readily differentiated according to their fruit and inflorescence. The fruit of Betuleae is a samara, while that of Coryleae is a wingless nut. Betuleae produce elongate, cone-like inflorescences, while Coryleae produce shorter and raceme-like inflorescences. These and other features indicate that Betuleae are the more primitive tribe. Within the tribe Betuleae, Betula is characterized as having solitary pistillate catkins which disintegrate when ripe (those of Alnus are clustered and persistent) (Hora 1981). The bark of Betula is often papery and peeling, with horizontally elongated lenticels. The leaves are alternate, pinnately veined, and doubly ser- rate. The trees are monoecious, with male and female catkins borne separately on an individual tree. Male catkins form in the fall and overwinter, while female catkins emerge in spring (Barnes & Wagner 1981). The Mountain Paper Birch has a samara with wings broader than the body, and scales on female flowers with the middle lobe prolonged (see Fig. 1). The leaves have hairs in the lower lateral veins beneath; the leaves are solitary on long shoots and in clusters of three on spur shoots. The variety cordifolia is char- acterized as having a cordate leaf base; moreover, the trunks tend to be more up- right, rather than leaning, and there may be a chromosomal difference between it and typical B. papyrifera. Location of Michigan’s Big Tree: From Glen Arbor, the tree can be located by taking M-109 west 2.2 miles to the stop sign in Glen Haven. From the stop sign, a left turn (south) leads about one mile to Harwood Road. If one turns right on 2002 THE MICHIGAN BOTANIST 95 FIGURE 1. Location in Michigan of the state and national champion and characteristics of the Mountain Paper Birch. The asterisk indicates the county where Michigan’s Big Tree is located. Illustration no. 1 is from Sargent (1922), where cordifolia as a separate species is recognized; illustrations 2–8 are from Barnes & Wagner (1981), of typical Betula pa- 1 pyrifera. 1. Flowering twigs (male left, female right) with leaves × ⁄2. 2. Fruit, samara, 1 ×5. 3. Winter twig, ×1. 4. Flowering twig, ⁄2. 5. Male flower, enlarged. 6. Silhouettes of female bracts, in winter, from three trees, ×1. 7. Bract with female flowers, enlarged. 8. Portion of winter twig, enlarged. Harwood Road and proceeds, the tree will be found near the roadside, along the second curve, about 0.4 mile down the road. Description of Michigan’s Big Tree: The circumference of the tree at four and a half feet above the ground was measured at 112″ (284 cm) [Diameter=36″ (91 cm)]. Its height was measured at 67′ (20.4 m), with a crown spread of 80′ (24.4 m). 96 THE MICHIGAN BOTANIST Vol. 41 INVITATION TO PARTICIPATE If you would like to join us in extending this series of articles by visiting and describing one or more of Michigan’s Big Trees, please contact Elwood B. Ehrle for help with locations, specifications for taking measurements, and assistance with the manuscript. The Michigan Botanical Club encourages your involve- ment in this activity. Please remember to ask permission before entering private property. LITERATURE CITED Barnes, B.V., & W.H. Wagner, Jr. 1981. Michigan Trees. A Guide to the Trees of Michigan and the Great Lakes Region. Univ. of Michigan Press, Ann Arbor. viii + 383 pp. Hora, B. 1981. The Oxford Encyclopedia of Trees of the World. Oxford University Press. Oxford, U.K. 288 pp. Sargent, C. S. 1922. Manual of the Trees of North America. 2nd ed. Reprint by Dover Publ. Inc. New York, NY. 1961. 2 vol. xxvi + 910 pp. Voss E. G. 1985. Michigan Flora. Part II. Dicots. (Saururaceae-Cornaceae). Bulletin of the Cran- brook Institute of Science No. 59 and University of Michigan Herbarium. xix + 724 pp..