MYCOSPHAERELLA 



215 



tree should be cut down and burned, as it never becomes free 

 from the disease. 



Farlow, G., Bull. Bessay Inst., 1875. 



Halsted, New Jersey Agric. Coll. Expt. Station, Bull. 78. 



MYCOSPHAEEELLA QOHANS.) 



Perithecia as in Sphaerella, asci i6-spored, without para- 

 physes ; spores elongated, i-septate, hyaline. 



Pear leaf spot. The early defoliation of pear-trees has for 

 long been considered to be due to the presence of a fungus 

 called Septoria piricola (Desm.). This has recently been 



I 



FIG. 62. Mycosphaerella sentina. i, pear leaf attacked by fungus, 

 nat. size ; 2, conidia of Septoria form ; 3, ascus and free spores of 

 ascigerous form. 2 and 3 highly mag. 



proved by Klebahn to be the conidial condition of the asci- 

 gerous fungus, Mycosphaerella sentina (Schroter). The injury 

 is undoubtedly caused by the conidial form of the fungus, the 

 ascigerous condition developing only on dead leaves that 

 have been lying on the ground throughout the winter. 



