132 DISEASES OF GLASSHOUSE PLANTS 
Attacked plants become very brittle and are easily 
damaged by the workers. In the worst cases the 
whole plant becomes covered with lesions and finally 
dies. 
Lesions in the pith and cortex are the characteristic 
internal features of the disease ; the walls of the attacked 
tissues are strongly browned, so that the patches are 
readily seen on splitting the stem with a knife. In older 
stems which have become hollow, small brown patches 
occur in the remains of the pith and in the cortex, but 
at the nodes, where the pith is close and moist, the 
patches are much larger. 
The roots are often found to be diseased only in the 
upper portion, and infection can usually be traced to 
some wound or insect puncture just below the ground 
level; the tissues of the lower roots are in these cases 
white and apparently healthy. In some cases, however, 
no wound can be discovered but the cortex is found 
to be browned to a considerable depth below the soil 
level, and microscopic examination shows the presence 
of the bacillus in the tissue. It would seem either that 
penetration of the root may occur without the aid of a 
wound or that the latter has escaped observation, or, 
on the other hand, that the disease has spread down to 
the root from an aerial infection. 
The disease is due to Bacillus lathyri Manns and 
Taubenhaus, described as the cause of “ streak ”’ disease 
of the sweet-pea, red clover, soya bean, etc. It has been 
shown that the organism from the tomato can cause a 
number of “stripe” or “streak” diseases of other 
plants. Positive results have been obtained with the 
following plants: sweet-pea, garden pea (Fig. 37), red 
clover, broad bean, lucerne, lupin, vetch, sainfoin, and 
potato. The symptoms of the disease upon these plants 
bear a strong resemblance to those on the tomato. The 
lesions are in the form of dry brown or black sunken 
spots, blotches, or furrows. 
The knowledge that “streak” disease of the above- 
