ioio Leaf Diseases of Celery. [march, 



inches across; gills white, becoming blotched with brown 

 here and there ; stem white, changing to brown when handled, 

 ring large. Flesh of cap and stem white at first, gradually 

 becoming tinged with reddish-brown, and changing at once 

 to that colour when cut and exposed to the air. 



It is found on the ground under trees, etc., in summer and 

 autumn, and has a delicate flavour. 



This species requires to be carefully distinguished from 

 deleterious allied species, which differ from it in the flesh not 

 changing colour when broken. 



"Celery leaf-spot" caused by Phyllosticta apii, Halsted, 

 was first observed in the United States in 1891, and since that 

 date it has repeatedly proved to be a 



Leaf Diseases of destructive parasite on celery. The 

 Celery. foliage is the part attacked, and the 



disease is readily distinguished among 

 the several leaf parasites of celery by the presence of one or 

 more large blotches on a leaf. These blotches are at first dull 

 brown, afterwards paler, dry, and studded with numerous 

 black points or perithecia, each containing numerous very 

 minute spores. When the spores are ripe the dead portion 

 of leaf on which they are produced crumbles and falls to the 

 ground, carrying along with it the spores of the fungus, which 

 infect the soil and prove a menace to following crops. 

 Numerous spores are also liberated at the moment of maturity, 

 and are conveyed By various agents to adjoining leaves, by 

 which means the djsease spreads with great rapidity during 

 damp, dull weather. During 1909 this fungus appeared in 

 Sussex under the form of an epidemic in a field of celery, 

 and much injury was experienced. 



A second celery leaf disease caused by a parasitic fungus 

 called Septoria petroselini, Desm., has been long known in 

 this country and on the Continent. In this instance the leaf 

 becomes studded with numerous small, irregularly angular, 

 brown spots, each bearing a few very minute black points or 

 perithecia, containing myriads of very slender needle-shaped 

 spores. As a rule when this fungus attacks celery an epidemic 

 results, due to the rapid production and dispersal of spores. 



