GOLDSTEIN: PLANTS AFFECTED WITH MOsAIC DISEASE 269 . 
material can be easily demonstrated by a few hours observation 
under the microscope of living preparations to which drops of the 
fixing solutions are added from time to time. Only the smallest 
thin crystalline plates will disappear entirely. 
Iwanowski has figured several somewhat amoeboid bodies, 
‘‘amO6ben erinnernde Plasmaanhdufungen,”’ attached to nuclei, 
as seen in sections of living material of mosaic infected tobacco 
leaves. He also observed the presence of the numerous crystal- 
line plates in the living cells, which in fixed material, according 
to his description, seemed to have disappeared entirely and 
given place to plates in which were imbedded small rod-like 
bodies. He concludes that these are plates of ‘‘bacteria,’’ or 
zoogloea formations, which are not seen in living cells save as the 
smooth crystalline plates. Their true nature therefore can only 
be demonstrated in fixed material. Iwanowski argues that 
amoebae could not possibly pass through bacterial filters. He 
maintains that the amoeboid bodies he found are only reaction 
products of the cells resulting from the continued irritation by 
the parasite, namely, the “rod-like bacteria’’ in the plates. 
hat seem to’ have been similar intracellular bodies have 
been described by Palm as occurring in the cells of tobacco plants 
affected with mosaic. Palm’s account of their occurrence and 
position in the cells agrees with what I find. He describes these 
bodies as frequently amoebiform, less frequently round to spheri- 
cal. In structure they may be decidedly reticulate, or show verv 
little structure at all. He finds there may be one or more cavities 
in the bodies which resemble vacuoles. He reports the bodies 
as not seeming to possess any automotive power though they 
change their position at times by the normal movement of the 
cell plasm. 
Palm accepts Iwanowski’s viewpoint as to the character of 
these amoeboid bodies, and also claims that small “granules”’ 
found in the cells of diseased tissue are the organisms responsible 
for the disease. 
In a preliminary report by Rawlins and Johnson on “ Cyto- 
logical Studies on Tobacco Mosaic,”’ these authors associate 
three different intracellular bodies with the disease. The first, 
a vellow striated mass of material, is no doubt the result of 
fixation and the fixing solutions upon the crystals found in fresh 
material as 1 have described above. The second type consists 
