Microscopic

Broadly ovoid, papillate sporangia in water

P. siskiyouensis oogonium with paragynous antheridium

P. siskiyouensis oogonium with amphigynous antheridium

P. siskiyouensis sporangium with lateral semi-papilla and subterminal, sub-basal insertion in the sporangiophore

Sporangia showing a variety of shapes and orientations of semi-papillae and sporangiophores

Sporangia of P. lateralis showing internal and external proliferation

Sympodial sporangiophore with external proliferation

Laterally intercalary chlamydospore of Phytophthora lateralis

Terminal chlamydospore on a short side stalk