CONIDIOPHORES WITH CONIDIA in dense conglomerations, grey-violet, felt, rarely loose, on the whole or a large area of the under leaf surface. On the upper surface of infected laves, indistinct, yellowish spots appear that later darken to pale brown.
CONIDIOPHORES (cp) 250-500 x 5-7 µm, not thickened or slightlythickened at the base, branched 4-6(-7) times.
Branches curved, with straight or beaklike final branches, slanted at a right or slightly obtuse angle, up to 17 µm long, 2-3 µm thick at the base.
CONIDIA (c) ellipsoidal or widely ellipsoidal, rounded at both tips or slightly sharpened at the base, pale violetish 17-28 x 15-20 µm.
OOGONIA. 32-40 µm, with a colourless or yellowish, thin wall.
OOSPORES 22-28 µm diam, with a thin, smooth episporium.
PLANT HOST AND DISTRIBUTION. Peronospora violae affects different plant species of the genus Viola growing in the whole Europe and North America (Kochman and Majewski 1970).
Kochman J., Majewski T. 1970. Grzyby (Mycota) IV. Glonowce (Phycomycetes), Wroslikowce (Peronosporales). Warszawa, 308 pp.