1 84 Apple "Scab" or "Black Spot." [June, 



infested is marked by dark brown or olive-green " sooty " 

 patches. Sometimes these patches are separate from one 

 another and very distinct — as in Fig. 2 ; at other times the 

 fungus follows more or less closely the veins or " nerves " 

 of the leaf on its upper surface (Fig. 3) ; in the case of other 

 varieties, again, the leaf, where it is attacked, forms on the 

 upper surface little swellings or eruptions, over which the 

 fungus spreads its dark brown spores (Fig. 4) ; or, finally, 



I ! 



fig. 2. — The Apple Scab or "Black Spot" fungus attacking the leaf. On 

 " Bismarck"; distinct "sooty" patches are formed on the under-surface (including 

 the midrib) of the leaf. A healthy leaf is shown to the right. 



the whole of the upper surface of the leaf may be coated almost 

 continuously with a very thin dark brown " sooty " covering.* 

 If a section of an apple leaf is cut across one of the " sooty " 

 patches on the leaf, and placed under the microscope, it 

 presents the appearance shown in Fig. 5. The spawn 

 (mycelium) of the fungus can be seen running between the 

 cells in the interior of the leaf (Fig. 56), where it feeds on 



* In some parts of Kent the disease on the leaves is known under the name of 

 "soot" or "sooty" fungus, but its connection with the "black spot" of the fruit 

 has not been recognised. 



