First person to use this name on MO: Gia-Phong Vu
Phytophthora infestans is the most famous species under the genus Phytophthora. It was well-known for causing an outbreak of potato blight or late blight in potato. The species is fungal-like Protist that belongs to the order Peronosporales (Class Oomycetes) which produces only one oospore when an oognium fused with antheridium.
Phytophthora infestans is unique because it has sporangiophores that are sympodially branched and and are of indeterminate growth. Sporangia has lemon-shaped and paillate. Sporangia are borne from the terminaal of sporangiophore tips.
Phytophthora infestans produces secondary zoospores that have two different flagellas: tinsel and whiplash.
The following image is taken from Wikipedia