Notes upon Celery. 203 



through the epidermis of the leaf to the tissues within, where they 

 spread and again cause the death of the affected parts, and conse- 

 quently the characteristic spots. Each hypha bears more than a 

 single conidium, and the scars or knees shown in the figure are 

 the points at which successive conidia were borne. The conidia 

 retain their vitality for some time, and it is feared that they may 

 be able quite generally to pass the winter without injury. 



Considerable confusion exists regarding the nature of the sea- 

 son during which this disease is most prevalent. It has been 

 reported most abundant during the hot, dry periods, and also 

 most injurious during the warm " muggy" days.* In my own 

 experience heat is an important factor, but moisture does not 

 necessarily give the celery plant the mastery. In hot dry weather 

 the vigor of the plant is reduced ; and, with heavy dews at night, 

 the action of the fungus is marked, especially on the lower leaves. 

 "With a wet soil and muggy days I have noted a rapid spread of 

 the fungus, and it is then that the disease will spread over large 

 areas of wilted or affected leaves. In a reportf of the Division of 

 Vegetable Pathology, it is stated that shade is of great import- 

 ance ; that where the soil is cool and moist, and the air humid, as 

 at Kalamazoo, Mich., the disease is said to be unknown. In this 

 connection the only observations I was able to make were upon 

 small areas in well drained, shaded, garden lots; and in such 

 locations the fungus was not abundant. This disease disappears 

 with the cool nights of autumn, and it may be followed by the 

 other blight discussed in this bulletin. Because this celery dis- 

 ease does not usually appear late in the season, and in order to 

 distinguish it from others, I have spoken of it as the early blight 

 of celery. 



Remedies. 



The use of fungicides for the prevention of the early blight has 

 been attempted wdlh varying success, but there is still lacking 

 much definite information about the use of these materials which 

 will necessitate some extended experiments during the ensuing 

 season. 



* Report U. S. Dept. Agriculture, 1886, p. 117. 

 t Report U. S. Dept. Agriculture, 1888, p. 398. 



