246 DISEASES OF ECONOMIC PLANTS 



fungus. These perforations are from 1-2 mm., or more, in 

 diameter, with irregular borders. Upon the midrib and 

 petiole depressed spots result. With small young leaves 

 distortion is produced, especially at the apex. The disease 

 appears to be limited to greenhouses and to be spread 

 largely by watering. 



It was first described by Selby ^ in Ohio in 1896 and has 

 since been noted in other states. 



Blight, septoriose {Septoria lactuccB Pass.) and (Septoria con- 

 similis E. & M.) . — Upon the old outer head leaves there often 

 appear very numerous, black pycnidia, so small as to remain 

 unnoticed unless by special search. The injury is usually in- 

 significant, though some dwarfing and curling of the leaf re- 

 sults. Upon seed plants these same diseases attack the leaves 

 with greater vigor, causing pale brown, discolored areas and 

 the death of the older leaves. Sometimes, through neglect 

 to destroy plants of the seed bed, these diseases may gain 

 such foothold as to cause injury in other beds. This can 

 usually be avoided by destruction of the seed-bed plants as 

 soon as transplanting is over. 



The diseases are not usually troublesome until late in 

 the season. The Trianon, Wonderful, and Salamander 

 varieties are very susceptible. The Boston is quite resistant. 



MUSHROOMS 



MycogoDose (Mijcogone pernidosa Magn.). — Though 

 noted in Germany as early as 1887 by Magnus, this disease 

 was not called to attention in America ^ until March, 1909. 



1 Selby, A. D., Ohio Agr. Exp. Sta. Bui. 73, December, 1896. 

 - Mrs. Flora W. Patterson, Am. Photopath. Soc, 1st annual meeting, 

 Boston, Mass., December 31, 1909. 



