THE ONIOJs^ SMUT 155 



cleaned, by carrying earth containing smut spores into 

 fields subsequently worked upon. Secondly, through 

 the adherence of the same smutted earth to the feet of 

 men and farm animals, and its consequent transportation 

 from one part of a field to another, or to different fields ; 

 an agency by no means unimportant. Thirdly, the 

 smut spores may be readily washed, with surface earth, 

 from higher to lower ground, as is a matter of common 

 observation. Fourthly, popular opinion to the contrary, 

 the spores being practically imponderable, may be readily 

 blown, with other dust-like material, either about the 

 same field, or into adjoining fields. The reason that 

 this mode of dissemination is of less importance than 

 some others lies, probably, in the fact that the spores 

 being formed and making their exit from the onion com- 

 paratively near to the ground, are readily washed into 

 it by rain, and have little opportunity for blowing 

 directly into the air, as is the case with corn smut, for 

 example." 



Treatment. — The simplest method of avoiding 

 injury by onion smut is to transfer the planting to new 

 land whenever the disease becomes destructive. But of 

 course this is only applicable either where one grows 

 only a comparatively small number of onions, or has a 

 large amount of land. 



It has already been stated that infection by smut 

 apparently takes place before the young plant appears 

 above ground. In the case of corn and other grain crops 

 affected by various species of smut, the fungus enters 

 the plant when very young. These facts would lead us 

 to suppose that if young onions were started in soil free 

 from smut, and then transplanted to smutty soil, they 

 would escape the disease, because the period of infection 

 has been passed. And such is said to be the case with 

 transplanted seedlings. Consequently, in the practice 

 of transplanting onions, — which is highly recommended 



