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SPORANGIA WITH SPORANGIOPHORES occur in conglomerations, forming grey-white, dense coatings on the under leaf surface. In plants infected systemically, the conglomerations of sporangiophores with sporangia occur on the whole area of affected organs. Systemically infected leaves become first yellow to dark brown, then roll, and finally die.
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Branches. Lateral branches 1-3(-5). Lower branches frequently produce branches of a second order. Terminal branches with two to four final branches, up to 20 µm long, 2-3 µm thick at the base.
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SPORANGIA (s) ovoid, widely rounded at both ends, with a thinner wall or a flat wart at the top, 15-25 x 14-21 µm.
OOGONIA 37-53 µm, with a yellow brown, up to 5 µm thick wall.
OOSPORES 25-40 µm diam, with a yellow brown, smooth or slightly roughened, up to 2.5(-5) µm thick episporium. Endosporium ca. 2 µm thick.
PLANT HOST AND DISTRIBUTION. Plasmopara densa affects species of the genera Bartschia, Euphrasia, Odontites, and Rhinanthus (Scrophulariaceae) growing in the whole Asia and Europe (Kochman and Majewski 1970).
REFERENCE
Kochman J., Majewski T. 1970. Grzyby (Mycota) IV. Glonowce (Phycomycetes), Wroslikowce (Peronosporales). Warszawa, 308 pp.