THE ONION SPOT DISEASE 157 



of whatever kind that is left on the field should be 

 burned as soon as ]3racticable, and, although onion land 

 is usually kept so clean that it cannot be burned over in 

 the fall, this practice will be found very advantageous 

 when it is possible. At the second and subsequent hand 

 weedings all onions which show smut in the second or 

 third leaf should be pulled, collected in a basket or other 

 convenient receptacle, and burned at once. This prac- 

 tice involves very little trouble, and the folly of leaving 

 the larger smutted onions to discharge crop after crop of 

 spores upon the ground, as the leaves successively 

 mature, is apparent ; especially when the enormous 

 number of spores thus formed is considered. It is 

 hardly an over-estimate to say that a single large onion 

 may mature during a season something like a cubic inch 

 of smut, which means between one and two thousand 

 millions of spores, each capable of producing a smutty 

 onion in the following season." 



Literature. — Dr. Thaxter's article so freely quoted 

 in the above account, will be found in the report of the 

 Connecticut Agricultural Experiment Station for 1889 

 (pp. 129-153). It contains numerous references to the 

 European literature of the subject. An earlier article, 

 by Professor W. G. Farlow, will be found in the report 

 of the Massachusetts State Board of Agriculture for 

 1876-77 (p. 164). 



The Onion Spot Disease 



Vermicularia circinans 



This is a fungus which has been described as inju- 

 rious to white varieties of onions after they are housed. 

 It starts in the field on part of the bulbs ; these produce 

 many spores, by means of which it is propagated in the 

 bins when the conditions are favorable ; that is, when 

 the atmosphere of the storage room is warm and moist. 



