6o6 
Journal of Agricultural Research 
Vol. XXVI, No. 12 
Like the rosette disease 6 , the leaf-mottled condition has not yet been 
readily reproduced under artificial conditions, and for this reason it has 
not been determined whether we are dealing with a true virus disease 
or whether the causal agent is transmitted by some soil insect or other 
soil organism of animal nature. 
The varietal ranges of the rosette and the leaf-mottled conditions are 
of interest at this point. Gut of 104 winter-wheat varieties and selections r 
grown on soil naturally infested with the rosette and leaf mottling causal 
agent or agents, only 9.6 per cent of the varieties or strains showed 
definite rosette, whereas 86.5 per cent showed leaf mottling in varying 
degrees of severity. In all cases varieties or strains showing definite 
rosette also manifested a definite leaf mottling. The small proportion 
of varieties and strains which are susceptible to the rosette disease isf 
unusual among plant diseases, and this relationship suggests a rather 
strong possibility that rosette may be a severe manifestation of a malady 
which has a wide varietal range and of which leaf mottling may be a 
milder expression. 
DESCRIPTION OF INTRACELLULAR BODIES 
Microscopic studies of both fresh and embedded material from the 
tissues of field-grown winter-wheat plants affected by the rosette disease 
have shown that certain cell inclusions are present in the crown tissue in 
the late winter and early spring. As the disease progresses, the bodies 
become more numerous and more generally distributed throughout the 
tissues of the plant. While the bodies are known to occur in the roots, 
throughout the crown tissue, in the leaf sheaths, and in the leaves, further 
studies may reveal them in other parts of the plants. As yet the bodies 
have not been found in plants known to be free from rosette or leaf 
mottling. 
In preparations from material killed and fixed in the usual botanical 
fixatives and stained with Flemming's triple stain, the intracellular bodies 
show a marked affinity for orange G. The bodies have shown only a slight 
affinity for safranin and much less for gentian violet. When preparations 
are stained with Heidenhain’s iron-alum haematoxylin the bodies tend 
to take the stain less intensely than the host nuclei, and in the destaining 
process the bodies generally lose the stain much sooner than the nuclei. 
The bodies usually occur singly in the host cells. Occasionally two or 
three are found in the same cell, but this seems to be the exception rather 
than the rule. Frequently the bodies are more abundant in tissues 
adjacent to internal lesions (PI. 3, B and PI. 4, B) of the crown tissue. 
Usually crown tissue containing intracellular bodies is of a yellow or 
yellowish-brown color even though definite internal lesions may not be 
present. 
In form, the bodies vary greatly. Round to oval are perhaps the most 
common forms, but it is not unusual to find bodies rather irregular in 
shape, as shown in the several plates. In long host cells it is common to 
find very long bodies such as the one shown in Plate 8, fig. 7. 
In size, the bodies range from much smaller to considerably larger than 
the host nuclei. In the case of bodies less than 2 to 3 microns in size, it is 
difficult to be certain of their exact identity. It is believed, however, 
6 McKinney, Harold H. investigations op the rosette disease op wheat and its control. In 
Jour. Agr. Research, v. 23, p. 771-800, 2 fig., 8 pi. 1923. literature cited, p. 799-800. 
