234 
Journal of Agricultural Research 
Vol. VIII, No. 7 
tive table is offered for the separation of species in the hope that it will 
aid other investigators in identifying the forms with which they work. 
This paper should be followed by others on parasitism, host relation¬ 
ships, and cytology of all forms that will throw light on the systematic 
relationship of the species. When these studies are completed, it will 
perhaps be possible to arrange a more natural classification. 
ECONOMIC IMPORTANCE OF THE GENUS PHYTOPHTHORA 
Although the actual number of species of Phytophthora is small, 
geographically they are very widespread, their presence having been 
recorded from the Tropics as well as the temperate regions, including 
Japan, India, Java, most of the countries of Europe, Australia, the East 
Indies, North America, and South America. Botanically, the hosts of 
Phytophthora spp. are distributed among 15 families, ranging from the 
Pinaceae to the Scrophulariaceae (16) 1 , and including plants of all ages 
and textures. On account of its omnivorous character, the injuries it 
causes are serious. These injuries include the damping-off of seedlings, 
spots on leaves, the rotting of fleshy tubers and rhizomes, and cankers on 
woody stems. The genus has attracted most attention through the attacks 
of one of the species on the common potato (Solanum tuberosum ). Al¬ 
though a number of our leading pathologists have devoted their best 
efforts to the study of this species, considerable work on its life history 
and cytology still remains to be done. 
The genus Phytophthora was founded by De Bary (1) on the potato- 
blight fungus. Up to the present time Saccardo has enumerated the 
following species of the genus: 
Phytophthora infestans (Mont.) De Bary (1). 
Phytophthora cactorum (Cohn and Lebert) Schroeter (31). 
[Peronospora cactorum Cohn and Lebert (18). 
Peronospora fagi Hartig (14, 15), Peronospora sempervii Schenk (30), Per¬ 
onospora omnivora De Bary (2)] 
Phytophthora phaseoli Thaxter (34). 
Phytophthora colocasiae Raciborski (25). 
The following species should now be added: 
Phytophthora nicotianae Van Breda de Haan (3). 
Phytophthora thalictri Wilson and Davis (36). 
Phytophthora syringae Klebahn (17). 
Phytophthora faberi Maublanc (19). 
Phytophthora arecae (Colem.) Pethybridge (23), (24). 
Phytophthora parasitica Dastur (10). 
Phytophthora erythroseptica Pethybridge (24). 
Another species, P. agaves Gandara, has been mentioned in literature 
(13); but as yet no description has been given, and no cultures have 
been distributed. 
1 Reference is made by number to “ Literature cited, ” pp. 373-276. 
