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Pomona College Journal of Economic Botany 



still hanging to the twigs. Entire twigs may thus be affected and the foliage 

 does not fall until it is thoroughly dead and dry. One can always tell this 

 stage by the dark color of the leaves. 



In all cases of doubt as to whether wither-tip is in an orchard or not, it 

 can be accurately demonstrated by placing the leaves or twigs, supposed to 

 be infected, into a moist chamber and within three or four days the cin- 

 namon-brown acervuli (Fig. 15) will appear on all surfaces in great numbers. 



Figure 15. At left a lemon leaf showing darkening area by incipient wither-tip; at 

 right the magnified surface of an orange leaf covered with numerous 

 acervuli of wither-tip, each one of which contains 

 great numbers of spores. 



Of the leaf-spot H. H. Hume writes in Bull. No. 74, Fla. Agrcl. Exp. Sta., 

 p. 164, Aug., 1904: "On the leaves, the disease first appears in the form of 

 rather irregular areas from one-eight to three-fourths inches across. Occa- 

 sionally they become confluent or join each other so as to embrace a large 

 portion of the surface of the leaf. The spots vary in color from bronze- 

 yellow to a dark shade of brown, depending upon the stage of development. 

 Usually the diseased spots are located near and extend to the margin of 

 the leaf. The tip is quite a favorite seat of infection, the lesions (diseased 



