454 



Journal of Agricultural Research 



Vol. IV, No. s 



collapsed parenchyma is evidence of their presence, and careful search 

 finds them lying closely appressed to the cell walls when they are not 

 abundant in the intercellular spaces. In this stage they are also in the 

 neighboring vessels of the leaf (fig. 2). In stained sections the walls of 

 the vessels often show injury by taking a deeper stain than normal ones, 

 even when the bacteria do not appear to have penetrated to their 

 interior. 



One leaf, which showed browning of some of the smaller veins, was 

 sectioned at various points on the veins and petiole. The bacteria were 

 numerous in the vessels of the browned area and for some distance 

 below, but thinned out downward so that none were found in the base 

 of the petiole or in the stem of the plant. In another case the bacteria 



Fig. I. — Section of nasturtiuin leaf four days 

 after spraying with suspension of Bacterium 

 solanacearum. Serially adjacent sections show 

 bacteria throughout the substomatic chamber. 



Fig. 2. — Cross section of a vein of nasturtium 

 leaf, showing vascular infection nine days 

 after spraying with suspension of Bacterium 

 solanacearum^. 



were traced in the vessels all the way from the wilting leaf blade to the 

 stem of the plant. Three plants in this set finally wilted completely. 

 An early stage of vascular occlusion and cavity formation in the stem of 

 a nasturtium, like that shown in Plate LXIII, is illustrated in figure 3. 



Several attempts to produce stomatal infection on tomatoes and tobacco 

 were made, but without success. 



SUSCEPTIBILITY OF THE NASTURTIUM 



From comparative needle-prick inoculations on nasturtium, tomato, 

 and tobacco with the Creedmore tobacco organism, which was beginning 

 to lose its virulence, it would appear that the nasturtium is very sus- 

 ceptible to infection by B. solanacearum, since it wilted readily, while 



