94 Agricultural Experiment Station, Ithaca, N. Y. 



color, small ix)imd patclies not larger than a pin-head make their 

 ai)])earance. These spots are pale greenish or grej'ish in color 

 and increase in size till in some cases they are half an inch aci^oss. 

 They are mostly ronhd, wdth a somewhat i>aler border. In older 

 specimens the patches are frequently confluent and of dark(n- 

 broAvn color. In very old specimens, specially in th.ose where the 

 fruit has undergone decomposition, the patches become black and 

 uneven. 



^' A miciioscopic examination of the small greyish spots showv^ a 

 iioarly colorless mycelium creeping over the surface. In the darker 

 portions of the large patches are septate hyphae or threads. In 

 some cases these come through cracks in the cuticle. The hyphae 

 are irregidar in outline and frequently bent. As the material 

 becomes older a dense stroma of short brownish hyphae appeal's. 

 This stroma lies between the cuticle and the cellulose layers of the 

 cell-wall. Under favorable conditions it keeps on producing the 

 erect septate hyphae which bears the slightest colored spores at 

 the end. The spores are oval in shape, pointed at the end, and 

 usually two-celled. On placing the spores in water they gei'mi- 

 nale in a short time, producing a colorless tube from one of the 

 cella. 



" The disease does not impair the quality of the fiiiit, as tJie 

 injury extends little beyond the spot, and affects only thi-ee or four 

 lavers of underhdng cells. These cells take on a brown color, 

 and have a slightly bitter taste. The greatest injury arises 

 through the cracks A^•hich are frequently' found in the older 

 patches, which allow other fungi, like the fruit-rot, to work their 

 ^Nay in. So it frequently happens that th.e rot accompanies the 

 scab. Tlie cladosporium or scab fungus causes the fi-uit to shrivel, 

 in severe attacks. 



" Here in centi'al Iowa I have observed this scab upon (lie fol- 

 lowing varieties: Speer, Ohippeway, Cheney', De Soto, KoUing- 

 stone, Maquoketa (Fig. 11), Pottawattamie and Miner. It appears 

 to be more or less local hei*e as well as elsewhere in the Unitetl 

 States. A coiTespondent has sent me specimens of the fungus on 

 Prunus Americana gi'own in Virgiuia. The disease has also 

 appeared in Canada, but principally on P. Americana, though in 



