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STATE BOARD OF AGRICULTURE 



one of them, the nature of the organism would be difficult to determine. 

 The organisms hold quite tenaciously to the haematoxylin stain, and if the 

 sections are mordanted for 6-8 hours in the iron-alum solution, after pro- 

 longed destaining they still will be stained deeply while all color will be re- 

 moved from plant structures except the nucleoli and chromatin. They are 

 not so numerous nor do they occur in an unbroken succession of cells as was 

 often found to be the case with the bean flagellates. They seem rather to 

 occur in "nests," that is, at a certain place in the stem or petiole they will be 

 quite numerous, then for a short distance they will not be found Several 

 individuals may lie in one sieve tube, then for the distance of several cells 

 none will be present. They have been found, however, in all parts of the 

 stem and petiole from which sections have been cut. 



Fig. 10. Photomicrograph of a sieve tube in a mosaic tomato plant showing a small trypanosome 

 passing- through a perforation in the sieve plate. X 1500. 



A. Sieve plate. 



B. Trjpanosome. 



Fig. 11 shows the typical trypaniform nature of the organisms as they are 

 found in the sieve tubes, while a broader type is seen in Fig. 12. An occa- 

 sional colony of very small individuals has been seen, the most interesting 

 case being where about eight apparently young individuals werejound lying 

 very close to a sieve plate. Division of some larger form or repeated division 

 of the smaller type had apparently produced the increased number. The 

 location of these very small individuals close to the sieve plates is correlated 

 with migration from cell to cell. These small forms have been seen passing 

 through the perforations in the sieve plates. In Fig. 10 is shown one of these 

 small organisms half way through one of these holes in the sieve plate. The 

 only type of division observed was b} fission. Ijongitudinal binary fission 



