Erysiphe europaea  

Mycelium on both surfaces of leaves, often ± evanescent.
Anamorph: conidia 28-38 x 13-17 µm, ± cylindrical, not formed in chains [fide Braun 1995].
Teleomorph: ascomata cleistothecia, scattered or in groups, 90-120 µm diam., oblate to globose, black when mature, composed of irregular polygonal cells to 18 (-25) µm diam. Appendages 4-6 (-10) in number, roughly equal in length to the ascoma diameter, hyaline, the apex branched dichotomously 3-4 times, usually ± recurved at the tips. Asci 66-73 x 60-64 µm, ± globose, rather thick-walled, splitting open to release the spores, usually 5- to 7-spored. Ascospores 20-23 x 15.5-17.5 µm, ellipsoidal, hyaline, aseptate, thin- and smooth-walled, without an epispore or gelatinous sheath.