Cytological Study of Living Cells of Tobacco Plants 
Affected with Mosaic Disease 
BESsIE GOLDSTEIN 
As one phase of a more extensive cytological study of the 
diseased cells in tobacco mosaic, as well as the mosaic of Solanum 
sculeatissimum and other plants, I have recently spent some 
time in the study of the now well-known intracellular mosaic 
bodies in the living condition. In epidermal and hair cells 
mounted in water, the bodies:are easily recognizable and can 
be studied for hours at a time under the immersion lens. 
The facts as to their structure, varying sizes and shapes, 
and their relation to the other contents of the cell are so definite 
and easily demonstrable, that I am presenting a number of figures 
illustrating their appearance in the living cell in advance of a 
more extended account of their appearance and behavior as 
shown in fixed and sectioned material. 
The epidermis of the diseased tobacco leaf is stripped off 
by the ordinary methods, and mounted in water. Material from 
the midrib and petiole is especially favorable, and such prepara- 
tions mounted under zero cover slips, can be easily studied with 
the 1/12’’ oil immersion lenses. The intracellular bodies are 
found in both epidermal and hair cells. I shall call them X 
bodies. : 
In such preparations, these X bodies appear at any parti- 
cular moment as oval or perfectly rounded or more or less 
amoeboid in outline, as in figures I, 2, and 5. They may lie in 
close contact with the nucleus, often as it were apparently 
wrapped around it, or they may be found in any other region of 
the cell. 
Internally they may be very coarsely and unevenly granular, 
or they may appear very evenly and finely granular as in figure 
2. They may contain several large vacuoles, or many small 
ones, as in figure 1. Sometimes the material of the body appears 
quite regularly alveolar as in figure 2. 
n figure 1 is shown an epidermal cell from the midrib in 
which the nucleus contains three nucleoli. Scattered through 
the cytoplasm are small chloroplasts. The X body lies in con- 
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