EXPERIMENT STATION BULLETINS. 



435 



found in diseased plants with those associated with bean mosaic. No meas- 

 urements were made but in size the clover organisms seem to conform with 

 those measured in the bean. 



Tomato Mosaic 



No great difficulty was encountered in locating, in the sieve tubes of tomato 

 plants affected with mosaic, organisms which, for this disease, are as con- 

 stantly associated and as tj^pical as the biflagellates found in bean and clover. 

 In longitudinal sections of stems and petioles, fixed and stained with the solu- 

 tions used in the study of bean mosaic material, these organisms are found 

 scattered along in the sieve tubes as deep-staining, long, sinuous, tapering 

 bodies, with one or both ends drawn out to a fine point, and usually with 



Fig. 9. Longitudinal section through phloem tissue of mosaic tomato plant. X 650. 



A. Two trypanosome-like organisms lying side by side in a sieve tube. 



B. Two of the organisms attached to each other by posterior ends of the body. 



probably the phenomenon of agglomeration. 



C. An organism apparently passing directly through walls of the sieve tube. 



D. Sieve tube. 



This ia 



one end larger than the other. There is great variation from long and slen- 

 der to short and relatively broad types, and individuals are present which 

 apparently are in various stages of development. Their location in the sieve 

 tubes is not constant but the majority of them lie in proximity to the host cell 

 nucleus. In all cases, however, the organisms lie in a plane parallel to the 

 longitudinal axis of the cell. For this reason cross sections of tomato are of 

 as little value, so far as finding the organisms is concerned, as are similar 

 sections from the bean, and if by chance a transverse section should sever 



