152 FUXGI AXD FUXGICIDES 



Professor Dudley a notice of it in Bulletin 15 of the 

 Cornell Station. 



The Onion Smut 



Urocystis cepulce 



The smut of onions has been known to occur in 

 America for about thirty years, although it was not defi- 

 nitely named and described by botanists until 1877. It is 

 widely distributed in the United States east of the Mis- 

 sissippi river, and appears to be especially destructive in 

 the onion-growing regions of Connecticut. Dr. Eoland 

 Thaxter, recently mycologist to the experiment station 

 of that State, has carefully studied the disease, i^iiblish- 

 ing an excellent illustrated account of it in his report 

 for 1889, from which the accompanying figures, and 

 much of the following information, are taken. 



According to Dr. Thaxter, *^the presence of smut 

 in onions is first indicated by one or several dark spots 

 at different heights in the leaves of seedlings, which are 

 seen to be more or less opaque when the plant is held up 

 to the light. These dark appearances may be seen in 

 the first leaf, before the second leaf has begun to develop 

 at all, and are more commonly found just below the 

 *^knee;" though they sometimes occur above it. After 

 a time, usually w^hile the second leaf is developing, lon- 

 gitudinal cracks begin to appear on one side of these 

 spots, which widen and show^ within a dry, fibrous 

 mass, covered with a black, sooty powder made up 

 wiiolly of the rijoened fruit or spores of the fungus, 

 w^hich are blown or washed out onto the ground. In 

 some cases the smut may appear only toward the upper 

 end of the first leaf, and become cut off from the main 

 body of the plant by the withering of the former. In 

 such a case an onion which has shown smut in its first 

 leaf appears, in some instances, to recover, showing no 



