EXPERIMENT STATION BULLETINS. ' 447 



organisms, located mainly in the sieve tubes and sieve parenchyma, have 

 been demonstrated to be constantly associated with these diseases. 



The bean and clover organism is a biflagellate, elongated protozoan whose 

 generic position is near Leptomonas. It apparently is a flagellate of new 

 generic rank, since the location and attachment of the flagella differ from the 

 structure in any knowTi genus. 



The organisms found in mosaic tomato plants apparently are trypanosomes, 

 or are closely related to this genus. They have been found only in the sieve 

 tubes. Their size varies from 6 to 30 microns in length and from 0.5 to 6 

 microns in width. 



In the sieve tubes of potato leaf-roll plants, organisms have been found 

 which more closely resemble trypanosomes than any other form. They are 

 usually closely associated with the host cell nucleus. These organisms are 

 also variable in size, some individuals being less than 1 micron wide and 12 

 long, while the longest one measured was 35 microns. 



All of these organisms lie in a plane parallel to the long axis of the cell 

 and have been demonstrated only in longitudinal sections. 



