P.cinnamomi was first described as the causal agent of stripe canker of cinnamomum burmanii in Burma. P .coinnamomi is listed in group VI.Sporangia are non papillate. They are tapered or rounded at the base, non caducous, and born terminally. P.cinnamomi is heterothallic. Oogonia are round opened with a tapered base smooth walled and hyaline. Antheridia are amphigynous.P. cinnamomi is a heterothallic species which forms sexual spores (oospores). This may require two mating types (A1 and A2) or an interspecific cross with the opposite mating type of another species such as P. cryptogea. The A2 type of mycelium can also produce oospores homothallically if provided with a stimulator substance released by host plant roots. Oospores are rarely produced in nature. Sporangia and encysted zoospores can survive in moist soil for several weeks but, in the absence of host roots, when soil water potentials and temperatures are sub-optimal for sporangial production, chlamydospores and possible oospores serve as survival propagules. Germination of chlamydospores is stimulated by organic nitrogen and some root exudates, but the conditions that influence oospore germination have not been determined. The optimum growth temprature for the species are 22-32.5 degree celcius.