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Images of red alder trees, catkins, root nodules and roots. (A) Red alder grove. (B) Male catkins. (C) Nodule clusters showing orange/brown pigments. (D) Roots from a 1-year-old Clone 639 red alder sapling. Photos credits: (A), Laurence B. Davin; (B), licensed through iStock.com (iStock.com/RomanKybus); (C), Qingyan Meng; (D), Tanya E. Winkler.
