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.