102 THE NEW ONION CULTURE 



Plowing in such refuse, or composting it, should 

 never be resorted to under any circumstances. 



The Onion V ermicularia {V ermicularia circinans 

 Berk) — The outer bulb scales of the white varieties 

 of onions, before they are harvested, are often attacked 

 by a black growth, quite inconspicuous at this time, 

 and composed usually of a central black dot, or small 

 ring, outside of which one or more larger rings are 

 arranged concentrically and with greater or less 

 regularity. When kept in a moderately moist, warm 

 atmosphere, this black appearance extends itself with 

 considerable rapidity, either growing in concentric 

 circles or successive wavy lines, or forming evenly 

 black areas on the bulb. At first this is confined to 

 the outer layer of scales ; but, as the disease extends, 

 it penetrates several successive layers, inducing decay 

 and often presenting an appearance, beneath the outer 

 layer, hardly distinguishable, at first sight, from the 

 onion smut. If the black rings and blotches are 

 examined closely they may be readily seen to be com- 

 posed of numerous black points of various size, single 

 or running together in clumps, and apparently made 

 up for the most part of very minute bristles. 



The economic importance of this disease rests 

 upon the fact that, although it does not as a rule 

 injure the onions seriously, or become conspicuous 

 upon them until after they are housed, it often attacks 

 them subsequently to such an extent as greatly to dis- 

 figure them, and impair thdr value for marketing 

 purposes. Some idea of the serious nature of the 

 disease may be inferred from the fact that one gentle- 

 man, whose statement is wholly reliable, estimates 

 his actual loss from this cause during the past season 

 at several thousand dollars. 



The fungus is introduced into the onion house 

 from the field, where it occurs not very abundantly 



