Fig. 5. Development of germlings from the untransformed P.p.n. strain in contact with solid surfaces. Freshly prepared zoospores were induced to encyst by vortexing and spread onto various surfaces. (A) Development on a cellophane membrane placed on top of water agar medium. After 40 hours, the spherical encysted zoospore (c) has germinated to form a germ-tube (asterisks) and two appressoria (arrowheads). A lobed structure (arrow) has emerged from the distal appressorium and has developed in a plane slightly out of focus. Note that the cytoplasm has migrated out of the cyst. (B) Development on the polystyrene surface of a Petri dish. After 20 hours, the encysted zoospore (c) produced a series of appressoria (arrowheads). No further development of different structures was observed after longer incubation. UC, ungerminated cyst. Bars, 10 µm.