NOTES ON PLANT DISEASES OF CONNECTICUT. 725 



The question whether or not the various forms of Exobasidium 

 found on the different genera of the heaths are distinct or not 

 has not been definitely decided. Often their macroscopic 

 appearance on different hosts is quite distinct, but as Richards 

 (Bot Gaz. 21 : 101. 1896) succeeded in producing the ordinary 

 leaf form from spores of the unusual large bladder form on a 

 different host, it looks to the writer as if these differences were 

 largely due to the age or parts of the host infected. Shirai 

 has described two species of Exobasidium on Rhododendron 

 indicum, to one of which our fungus possibly may belong if 

 they are really distinct, though the spore measurements do not 

 seem to agree entirely. 



CELERIAC, Apium graveolens var. rapaceum. 



LEAF BLIGHT, Cercospora Apii Fr. We have reported before, 

 on ceieriac, the leaf spot due to Septoria, but not this fungus. 

 Both produce brownish or grayish spots of considerable size 

 on the leaves, often causing them to turn yellow and die pre- 

 maturely. They are often found associated, the Cercospora 

 being distinguished by its minute threads arising from the 

 surface of the leaves, while the Septoria forms small, embedded, 

 black specks. 



CHESTNUT, Castanea sps. 



CHESTNUT BARK DISEASE, Diaporthe parasitica Murr. Speci- 

 mens of this serious disease of our native chestnuts have been 

 collected on the Japanese chestnut, Castanea japomca, in a local 

 nursery. Dr. R. T. Morris, who grows a large number of 

 varieties of chestnuts on his Stamford farm, also reports (Conn. 

 Farmer, March n, 1911, p. 2) that, besides the Japanese species, 

 the European species, Castanea sativa, and the American Chin- 

 quapin, Castanea pumila, have been more or less subject to this 

 blight at this place. See page 716 of this Report. 



CHESTNUT, Castanea dentata. 



POWDERY MILDEW, Microsphcera Alni (Wallr.) Wint. We 

 have not reported this host because we have found the mildew 

 on it previously only in the woods, but in September, 1907, 

 it was observed on cultivated trees in a small nursery at Storrs. 

 It forms evident, mealy, whitish growths, in which the perithecia 



