3ul. 1118, U. S. Dept. of Agriculture. 



PLATE XIV. 



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Citrus Scab on the Leaves of Rough Lemon. 



Fig. 1. — Photomicrograph of cross section of emerging leaf infected with citrus scab. 

 Three distinct lesions are seen on the lower or exposed siu'face. The arrangement 

 of the leaf in tlie bud probably accounts for the relatively small number of lesions 

 found on the upper surface of affected leaves. Fig. 2. — Photomicrograiih of citrus- 

 scab lesion on expanding leaf. Such lesions can sometimes be seen faintiv with the 

 unaided eye. The leaf tissue is ali'ected to a depth of two or three cells, even before 

 the leaf expands. Notice the stromatic mass of fungal hyphfe. Fig. 3. — Photomi- 

 crograph of a citrus-scab lesion on expanded leaf. This lesion, probably 2 months 

 old, is being overrun by a saprophj'tic Cladosporiiun. The scab fimgus penetrates 

 the host tissue intercelllilarly for some distance. 



