Uromyces geranii
Spermogonia amphigenous, few, 135-150µ diam., orange, becoming darker.
Aecia hypophyllous and on the petioles, on the leaves chiefly in the vicinity of the nerves and there forming large dense clusters to 2 cm long, on thickened spots and often causing distortion, at first closed and hemispherical, then opening with a circular pore, at length with a slightly revolute, incised margin; orange. Peridial cells not firmly connected, overlapping, outer and inner walls of equal thickness (3-4 µm), the inner wall with small warts often joined in small rows. Aeciospores 24-33 x 18-26 µm, ovoid to ellipsoidal, the wall yellow, ca 2µm thick, densely and minutely verruculose, contents orange.
Uredinia hypophyllous, generally on brownish or reddish-yellow spots, scattered or gregarious, sometimes in circinate groups, minute, rounded, pulverulent, cinnamon, surrounded by the cleft epidermis. Urediniospores 20-30 x 18-26 µm, globose to obovoid, brown, the wall 2 µm thick, sparsely echinulate, with 1, rarely 2 equatorial pores.
Telia similar but less pulverulent, blackish-brown. Teliospores 22-42 x 13-25 µm, subglobose to obovoid, the wall not thickened above, with an apical pore covered by a hyaline papilla up to 7 µm high, smooth, brown, pedicels short, hyaline, deciduous.
Not formally assessed, but common and very widespread.
On living leaves of Geranium species, including G. dissectum, G. himalayense, G. molle, G. pratense, G. pyrenaicum, G. robertianum, G. rotundifolium and G. sylvaticum.
Throughout the British Isles, including Ireland and the Channel Is.