•31- 



significant problems in processing tissues. Glutaraldehyde 

 fixation is necessary to preserve the configuration and banding 

 of the inclusions in CyMV-inf ected tissues. 



Viruses infecting orchids other than those included in 

 this study have been described, such as Cymbidium ringspot, a 

 tombusvirus (Hollings and Stone, 1977; Hollings et a_l. , 1977; 

 Matthews, 1982). Distinctive inclusions induced by this virus 

 have been described (Russo and Martelli, 1981; Martelli and 

 Russo, 1981). Light microscopy should also be useful in 

 detecting this virus as well. Dendrobium vein necrosis virus, 

 whose properties are similar to those of closteroviruses , 

 should form fibrous and banded-body inclusions in phloem tissue 

 (Lesemann, 1977; Matthews, 1982). These types of inclusion can 

 be detected by light microscopy (Christie and Edwardson, 

 1977) . 



The specific identities of the rhabdoviruses infecting 

 Brassia and Cymbidium described herein have not been 

 established. The particle dimensions and spokewheel-like 

 configurations are similar to those described for the third 

 subgroup of plant-infecting rhabdoviruses (Matthews, 1982), but 

 their relationship to one another and to the viruses examined 

 in this study remain to be determined. The cylindrical 

 inclusions of bean yellow mosaic virus noted in this study 

 conform to those belonging to "subdivision II" (Edwardson, 

 1974). However, BYMV cylindrical inclusions and dense bodies 

 occurred rarely in Masdeval lia tissues, indicating that they 



