8 SOME FUNGOUS DISEASES OF ECONOMIC IMPORTANCE. 



DESCRIPTION OF THE FUNGUS. 



The fungus Kawakamia cyperi (Miyabe and Ideta) Miyabe was 

 first tentatively described as Peronospora (?) cyperi M. and I. in 

 Ideta's Lehrbuch der Pflanzenkrankheiten in Japan, page 122, figure 

 20. Later, Miyabe decided to establish a new genus, Kawakamia. 

 This genus was fully described in the Botanical Magazine of Tokyo, 

 Vol. XVII, No. 202, page 305. The name was given in honor of Mr. 

 T. Kawakami, who succeeded in finding the conidial stage and its 

 method of germination. 



The material first received at the Bureau of Plant Industry showed 

 no external evidence of the fungus, but there were slightly depressed 

 brown areas which resembled more a condition caused by malnutrition 

 than by a fungus. Numerous sections were made of the diseased por- 

 tion of the stem and comparatively little mycelium was found to be 

 present, but a few oospores being observed led to the suspicion that 

 the fungus might be the cause of the trouble. In more material re- 

 ceived at a later date, a few conidia were found, while a third collec- 

 tion showed the fungus still more luxuriantly developed. 



In the discussion of this fungus Doctor Miyabe remarks that the 

 species is nearly allied to Phytophthora, but differs from it in the 

 conidia possessing a prominent beak and a peculiar pedicel cell which 

 persists as an appendage. The American specimens differ from 

 Doctor Miyabe's species in the measurements of the conidia, but agree 

 in all other essential respects. In the description by Doctor Miyabe 

 the maximum dimensions of the conidia are given as 68 by 32 /*, 

 while those studied by the writers of this paper are 130 by 30 /x with 

 the beak included, the beak being 15 by 9 fx. It is difficult to get 

 a conidium with the beak attached, as the beak is extremely fugacious, 

 breaking off and leaving the spore with an abrupt, flattened apex. 

 The progress of the disease was accompanied by a characteristic 

 change in the color and turgidity of the diseased plant. In the very 

 early stages the affected culms were bright yellow; as the disease 

 developed they became reddish brown and wilted, changing in the 

 most advanced stages to dull brown and showing a considerable col- 

 lapse of the cell tissue. The conidia developed only in the later 

 stages and appeared as a white, cobwebby mass on the diseased 

 brown areas. 



Kawakamia cyperi appears to be parasitic on Cy perns tegetiformis 

 only; at least it has not been reported on any other species of 

 Cyperus. Several sedges have been introduced by the Department 

 of Agriculture, but no other parasite of importance has been 

 observed. 



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