Pkthybuidge ANI1 MuKPHY — Bacterial Disease of the Potato. 37 



EXPLANATION OF PLATES. 



Plate L 



Fig. 1. A large plant with several stalks all attacked with Black Stalk-rot, 

 with a background of healthy plants. Variety, " British Queen." 

 Photographed in July. 



Fig. 2. The " heel " or proximal end of an affected tuber, showing the dis- 

 coloured diseased area on the skin and prominent lentieels. Variety, 

 " British Premier." 



Fig. 3. An attacked tuber cut longitudinally, showing the blackened diseased 

 tissues with cavities in them situated at and spreading from the heel 

 end. The tei'minal " eye " has produced a short sprout. Variety, 

 " Clifden Seedling." 



Plate IL 



Fig. 4. A single affected stalk, .showing the almormal foliage and decay at its 

 base. Variety, " Champion." 



Fig. 5. A tuber which was artiiicially inoculated with B. melanogenes split 

 longitudinall}', showing the progress of decay at the stab and in the 

 " vascular ring." 



Plate III. 



Fig. 6. A potato plant inoculated with B. melanogenes. The left-hand 

 diseased stalk was inoculated below the present surface of the soil ; 

 the right-hand still healthy stalk was not inoculated. Variety, 

 " Champion." 



Fig. 7. Four slices of living potato prepared under aseptic conditions, showing 

 four days' growth of B. melanogenes. 



B.I. A. PROC, VOL, XXIX., SECT, B. [F] 



