310 GREENHOUSE MANAGEMENT. 



indicates, it produces spots upon the foliage which at 

 first are not larger than the head of a pin, but increase 

 in size until a third, of a leaf may be included in a single 

 spot. As there are other distinct species of fungi that 

 produce leaf spots upon the violet foliage, it is necessary 

 to place some stress upon the characteristics of the cer- 

 cospora spot. 



When the microscope is used upon the spots it is 

 seen that the blanched surface of the leaf is covered with 

 small tufts or rosettes of irregular brown threads. This 

 fungus produces its spores outside of the infested tissue 

 and the spores are thus in easy reach of any fungicide that 

 may be applied to the surface. This Cercospora is closely 

 related to the one upon the celery {Cercospora apii,Yv.) 

 and no doubt can be controlled in the same way by the 

 use of the compounds of copper. 



violet leaf spot no. 2 (Phyllosticta Violce, Sacc). 



A second form of leaf spot of the violet can be dis- 

 tinguished by the naked eye. The spot is remarkably 

 white and breaks near the margin, which consists of a 

 ring of a cream color. Very often the central portion of 

 the spot has disappeared, leawng the affected leaf with a 

 number of holes. If viewed closely, the thin, white cen- 

 tral portion of the spot is seen to contain a number of 

 minute specks that are imbedded in the thin substance 

 of the dead tissue. The spores, as the moisture dries 

 away, are carried by the moving currents of air and fall- 

 ing upon healthy leaves produce, shortly, new spots of the 

 disease. This fungus needs the same treatment as the 

 Cercospora, and as they often grow together upon the 

 same leaf, the spraying for the one will answer for the 

 other. 

 violet leaf spot no. 3 (Ascocliyta Violce, Sacc). 

 Somewhat like the last described leaf spot is one 

 that is caused by a species of Ascochyta. This is quite 



