TECHISriCAL BULLETIN" J^o. 4. 



DEPARTMENT OF BOTANY. 



DEVELOPMENT AND PATHOGENESIS OF THE 

 ONION SMUT FUNGUS.^ 



BY P. J. ANDERSON. 



I. Introduction. 



Onion smut is the most destructive of all onion diseases in New Eng- 

 land. In the Connecticut Valley it is probably responsible for more loss 

 to the growers than all the other diseases of this crop combined. Despite 

 the fact that a method of control by the use of formaldehyde has been 

 developed, manj'- fields are now planted to other less profitable crops on 

 account of the ravages of smut; every year sees fields plowed up because 

 smut has so reduced the stand that it is not worth while to tend them; 

 more important in the aggregate, perhaps, is the smaller toll which the 

 disease exacts from each onion grower throughout considerable sections 

 of the valley. 



Investigation of the disease yviih the primary object of finding better 

 methods of control was begun by the Department of Botanj'- of the Massa- 

 chusetts Agricultural Experunent Station in 1918, and has been continued 

 to date. Since control measures are necessarily conditioned by the nor- 

 mal life history of the pathogene, and since a review of the published re- 

 search of other investigators showed that the development of the fungus 

 had been inadequately^ studied, this phase of the problem has been made 

 the subject of no inconsiderable part of the writer's stud3^ Results of the 

 work which deals directly with control are to be presented in another 

 pubUcation. The present paper concerns certain phases of the life cycle 

 of the causal organism {Urocystis cefXilae Frost) in which it seemed to the 

 writer that further investigation was desirable. Beginning mth germina- 

 tion of the spores, the development of the fungus will be followed through 

 its saprophytic stage, infection of the host, distributive stage within the 

 host and final sporogenesis. 



• This paper embodies the results of preliminary and fundamental work on a project having 

 for ita chief aim the control of onion smut. A report on the more practical phases of this project 

 is to be published shortly. 



