6 RELATION OF CEOWN-GALL TO LEGUME INOCULATION. 



crops greatly magnify the severity of nematode infection for suc- 

 ceeding crops in regions where this pest occurs, and this analogy 

 emphasizes the necessity, at least until the lack of the necessity for 

 such caution has been demonstrated, of using the utmost care in 

 guarding against the dissemination and the favoring of crown-gall 

 through the agency of these crops. 



LOCALITIES WHERE CROWN-GALL HAS BEEN FOUND. 



At this time we have records of the occurrence of crown-gall 

 tumors upon alfalfa in central Kentucky, southwestern Alabama, 

 northern Virginia, southern Maryland, and northern Pennsylvania. 



In greenhouse plants grown at Washington, D. C, in infected soil 

 received from Kentucky, alsike clover, crimson clover, red clover, and 

 alfalfa showed extensive infection, and it is probable that these 

 plants will be found naturally infected in different parts of the 



United States. 



CONCLUSIONS. 



(1) The crown-gall organism has been found in tumors somewhat 

 resembling the normal nitrogen-fixing nodules upon the roots of 

 alfalfa, crimson clover, and alsike clover. 



(2) Great care should be taken in using soil or cultures for inocu- 

 lating legumes in regions which may eventually be used for sugar 

 beets or for orchards. 



(3) It is usually possible to distinguish the tumor produced by the 

 crown-gall bacteria from the nodule formed by the nitrogen-fixing 

 bacteria by their external appearance. 



(4) By the use of special media it is possible to distinguish between 

 the bacterium which causes crown-gall and the nitrogen-fixing bac- 

 terium which forms the desired nodules upon the roots of leguminous 

 plants. 



(5) It is not known what other leguminous crops are susceptible 

 to crown-gall infection. It is believed, however, that there is reason 

 to suspect all of the clovers. 



Approved : 



James Wilson, 



Secretary of Agriculture. 



Washington, D. C, March 17, 1911. 



[Cii. 76] 



O 



