Pethybkidgk — Observations on Phytophthora erythroseptica. 197 



ammoniaoal copper hydrate. It is probable that an extremely thin layer of tliis 

 material covers the whole surface of the conidium. 



The couidia (zoosporangia) may germinate either by producing germ- 

 tubes direct or by the formation of zoospores. The details, which do not 

 differ essentially from those observed in other species of Phytophthora, are 

 described. 



The oospores have been caused to germinate after a suitable period of 

 rest. Previous to the production of a germ-tube by the oospore, which then 

 penetrates to the exterior through the oogonial wall, the thick inner portion 

 of the wall of the oospore dissolves and appai'ently serves as a store of reserve 

 carbohydrate food material. 



Whereas formerly the reproductive organs of the fungus had only been 

 observed in artificial pure cultures of the fungus as a saprophyte, they have 

 now been found in all of the underground parts of the plant, including in 

 one case a tuber. 



Plants in the roots, rhizomes, stems, and tubers of which the fungus has 

 been found, exhibit symptoms of disease in their sub-aerial organs, and it 

 is believed that these symptoms, which are of the " wilt " type, are due to the 

 invasion of the plant by the parasitic fungus. Hence the name " Pink-Rot 

 Wilt " is suggested for the disease. 



The disease is evidently contracted from tlie soil, and is of serious 

 consequence only in land which has borne a crop of potatoes for several 

 successive seasons. 



December, 1913. 



[ExPLANAnON OF PlATE. 



