Betula murrayana

Betula murrayana commonly known as Murray birch, is a critically endangered species of small birch that is endemic to Washtenaw County, Michigan in the United States and St. Williams, Norfolk County, Ontario, in Canada.

Description
The tree can be up to 15 meters in height and usually has several trunks. The bark of the mature trees is usually dark red-reddish brown and has horizontally-expanded lenticels. Its leaves are 5–11 centimeters × 3–6 centimeters.

Taxonomy
It was named by Burton V. Barnes and Bruce P. Dancik, in Canadian Journal of Botany 63(2):223-226, in 1985. The specific epithet honors Frank Murray, the person who discovered the Michigan population of the species. Betula murrayana is an evolutionarily recent species that arose through hybridization between Betula alleghaniensis and another hybrid, Betula × purpusii (a hybrid of B. alleghaniensis and Betula pumila). Betula murryana has a chromosome number of 2n=112, while B. alleghaniensis has 2n=84, B. pumila has 2n=56. and B. × purpusii has 2n=70.

Conservation
Only two sites are known. The Ontario population has not been re-located, despite searches, and its status is unclear. The Michigan population has only one surviving non-cultivated individual. However future populations may be discovered along the Great Lakes or St. Lawrence Valley, as there are many areas where the parent species overlap, and the species is a natural hybrid.

The Holden Arboretum, the University of Michigan, and Matthaei Botanical Gardens all have propagated seedlings from cuts of the Michigan individual, which could be used to conserve this species if it is faced with extinction.