| James Robert Weir | |
| Birth Date: | 1882 |
| Birth Place: | Scottsberg, Indiana |
| Death Date: | 1943 |
| Thesis Title: | Untersuchungen über die Gattung Coprinus |
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| Thesis Year: | 1911 |
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| Author Abbrev Bot: | Weir |
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James Robert Weir (1882–1943) was an American mycologist specializing in wood decaying fungi and forest pathology. He advised Henry Ford on rubber plantations and was head of The U.S. National Fungus Collections.[1]