2\4 



DISEASES OF CULTIVATED PLANTS 



conidia elliptical, olive, about 16 /x long. Pycnidia resembling 

 the perithecia, containing elliptical pale yellow, 3-septate 

 stylospores, 10-12x6-7 /*. Spermogonia also similar to the 

 perithecia, producing very minute spermatia. Perithecia 

 crowded, asci cylindric-ovate, 110-150x16-18 fi; spores 





] IG. 61. Plowrightia morbosa. 1, portion of a plum 

 branch, showing conidial stage of the fungus; 2, branch 

 with ascigerous condition of the fungus ; 3, conidiophores 

 bearing conidia ; 4, ascus containing 8 spores. Figs. 1 and 

 2 reduced ; rest highly mag. 



obvate, hyaline, 1 -septate, basal cell much the smaller of the 



two, 15-20 X 8-IO /*. 



The only practical method of dealing with this disease is 

 to cut out all diseased knots. When the tree is badly 

 infected, new knots frequently develop at or near the points 

 from which knots have been cut away. In such cases the 



