Bui. 1118, U. S. Dept. of Agriculture. 
PLATE XIV. 
gv 
,#" 
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 surface. The arrangement 
of the leaf in the bud probably accounts for the relatively small number of lesions 
found on the upper surface of affected leaves. Fig. 2.— Photomicrograph of citrus- 
scab lesion on expanding leaf. Such lesions can sometimes be seen faintly wi1 h the 
unaided eye. The leaf tissue is atl'ected to a depl h of two or three colls, even before 
the leaf expands. Notice the stromatic mass of fungal hyphse. Fig. 3. — Photomi- 
crograph of a citrus-scab lesion on expanded leaf. This lesion, probably 2 months 
old, is being overrun by a saprophytic Cladosporium. The scab fungus penetrates 
the host tissue intercellularly for some distance. 
