THE BROWN ROT OF SOLANACEAE : TYPE 



179 



occur also on nasturtium stems. On tobacco, longitudinal black 

 sunken stripes appear on the softer stems and large, irregular 

 brown spots on the leaves, especially on the basal "ears" of 

 the leaf. The tobacco leaves also frequently show brown veins. 

 Compare \vith the Black Rot of Crucifers (No. II). 



FIG. 121. FIG. 122. 



FIG. 121. Young tomato plant: left-hand shoot inoculated at X by needle- 

 pricks introducing Bacterium solanacearum; right shoot pricked with a sterile 

 needle. Photographed at end of 5 days. Terminal leaves of inoculated shoot 

 wilting and lower leaves reflexed. The inoculated stem begins to show incipient 

 roots while the other is free (see Fig. 122). 



FIG. 122. Part of left and right branch of Fig. 121 after 12 days. The 

 branch showing the incipient roots was inoculated on the two nodes immediately 

 above the part here shown. The smooth branch was pricked with a sterile needle 

 in the internodes here shown. 



On all of the host plants, the foliage wilts more or less, often 

 completely, the occluded vessels are usually stained brown or 

 black, and there is often an extensive destruction of pith and 

 bark, so that in tomato and tobacco the stem may be honey- 

 combed for long distances with bacterial cavities. Sometimes 



