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KANSAS UNIVERSITY QUARTERLY. 



The genus Picccitiia embraces some of the most ubiquitous 

 parasites. Sixty-three of its species are catalogued in the Host 

 Index on grasses alone. To the unaided eye the presence of this 

 class of parasites is indicated by elevated streaks or spots of a 

 yellow, brown or black color. Discolorations sometimes extend from 

 these well-defined areas, but usually the healthy color of the tissues 



about them is preserved. Fig. i, plate XI, illustrates thin sections 

 through a leaf of Eriophorum virginiciwi parasitized by Puccinia 

 angustata. The group of spores is seen to arise between two fibro- 

 vascular bundles. The cuticle of the inner surface together with 

 some of the parenchyma cells has been pushed up and broken, permit- 

 ting the spores to protrude above the surface of the leaf. It is the 

 protruding line of spores extending along the leaf between the fibro- 

 vascular bundles that reveals so clearly to the naked eye the presence 

 of this class of fungi. The mycelium from which the spores arise 

 penetrates to the upper cuticle and is apparently confined on either 

 side by the fibro-vascular bundles. The mycelium is seen through 

 the colorless cuticle of the upper surface as brown streaks and spots. 

 The parenchyma in E. virginicnm is arranged in two or three com- 

 paratively dense layers against the upper and lower cuticles, while 

 between these layers and the fibro-vascular bundles the parenchyma 

 is open and spongy. This is shown more clearly in sections of unaf- 

 fected leaves. The spores of the fungus are developed in the central 



