44 



EXPLANATION OF ILLUSTRATIONS. 



TEXT FIGURES. 



Fig. 1. Porfion of a bull) scale from plant No. 20. inoculated February 7, drawn 

 June 14. showing four health}- and four diseased vascular bundles. The 

 parenchyma between two of the latter has largely disappeared, its ■olace 

 being occupied by a cavity full of bacteria. Smaller cavities in the paren- 

 chyma, close to the vascular tissue, are visible in each one of the diseased 

 bundles. The bundle in the middle of the scale also shows the bacterial 

 occupation of anastomosing veinlets. The diseased portions w^ere bright 

 yellow from the presence of enormous numbers of the parasite, which, how- 

 ever, had not reached the surface of the scale. The infection of this scale 

 was from below upward. (Page 22.) 



Fig. 2. Leaf of plant No. 25, inoculated February 7, drawn April 80. The figure 

 shows shriveled apex and dead central stripe, na-row border of yellow, and 

 beyond this to either side healthy green tissue (white in the figure). In the 

 yellow border on the right side are some dotted areas intended to represent 

 water-soaked tissue: i. e., spots recently invaded apparently by a slow side- 

 wise movement of the bacteria from the central stripe. ( Page 23. ) 



Fig. 3. Slant. 30 per cent, cane-sugar agar showing the '• shagreen '" surface. 

 Culture No. 9. June 30, 1898. Photographed August 2. (Page 38.) 



Fig. 4. Enlarged diagrammaticverticalandhorizontalviewof a similar shagreen 

 surface from a sweet-potato culture twenty days old. (Page 38.) 



Fig. o. Fermentation tube showing behavior of Ps. hyacinthi in peptone water 

 or peptonized beef broth with various carbohydrates, e. g., grape sugar, 

 fruit sugar, cane sugar, milk sugar, galactose, mannit, glycerin, ethyl alco- 

 hol, etc. Maltose is a possible exception, tubes with this sugar having 

 finally clouded very feebly in th'^ closed end. None yielded any gas. ( Page 41. ) 



Fig. 6. Stab culture in gelatin + 10 jjer cent cane sugar inoculated Febrnary 

 10. On March 14 there was a well-developed stab and a good surface growth, 

 but no liquefaction, the curved surface being due to the drj'ing out of 

 the gelatin. On April 12 the gelatin had dried out as indicated by the 

 dotted line, but there was no liquefaction. (Page 42.) 



PLATE FIGURES. 



Fig. 1. Cross section of the bulb of plant No. 8, inoculated in the upper part of 

 the scape February 16. 1897. Photographed June 23, 1897. Six vascular 

 bundl( s broken down and filled with the bright yellow bacterial slime. 



Fig. 2. Onion leaf, inoculated January 29. 1898. Painted by F. A. Walpole, 

 March 5. The yellow color of the leaf in the vicinity of the inoculations 

 was due to the slow and long-continued growth of the organisms: i. e.. it is 

 the yellow color of the bacteria showing through. 



Fig. 3. Leaf of plant No. 51 (series 9). inoculated near the apex (at x) on Febru- 

 ary 11. Painted by F. A. Walpole, .March 5. The water-soaked lines shown 

 in the lower pai't of the stripe were conspicuous. This leaf was injected 

 with 0.3 cc. of a cloudy beef-broth culture eight days old, but there were no 

 sj'mptoms until after the sixth day. 



Fig. 4. Leaf of plant No. 52, inoculated at the same time, from the same culture, 

 in the same manner, and with the same quantity of broth as No. 51 (fig. 3). 

 Painted March 5 by F. A. Walpole. Symptoms farther advanced than in 

 fig. 3, but none visible the first week. 



Fig. 5. Cross section of the upper part of the bulb of plant No. 63, inoculated 

 February 12, 1898. through the flowers. Photographed June 18. Eight 

 scales visibly affected (16 vascular bundles). Farther down, near the junc- 



