Chrysomyxa rhododendri . a–d. On Picea abies: a. Needles with primary aecia; b. Inside of peridial cell of primary aecium; c. Single primary aeciospore with a longitudinal groove-shaped overlay with warts (ornaments) underneath (arrow); d. Annulate ornaments at higher magnification; e–g. On Rhododendron: e. Groups of orange-yellow secondary aecia (uredinia) on Rh. ferrugineum; f. Telia on Rh. hirsutum; g. Median section through a telium with a few teliospores starting germination; (a by Walter Obermayer; b from Klebahn 1914: 692; c, d from Zwetko and Blanz 2018: 276, 280; e, f by Julia Kruse; g from Dietel 1928: 44, after De Bary, with permission from Duncker & Humblot GmbH).