398 



BACTERIAL DISEASES OF PLANTS 



reticulate or fish-scale inner structure, or an opaque white center 

 with a translucent margin. On gelatin the marginal growth 

 of surface colonies or streaks is unlike that of the body of the 

 colony, being undulate-erose, frilled, lobed or incised (Figs. 311 

 and 312). With 1 per cent dextrose added to the gelatin the 

 colonies are frequently ring-marked (Fig. 313). In +15 bouillon 

 there is a thin clouding but no rim, pellicle or flocculence during 

 the first 4 days; later there is or may be a thin pellicle. In 

 neutral bouillon no rim or pellicle was observed. In undis- 

 turbed tubes of 2 per cent Witte's peptone w r ater after 5 or 6 

 days there is a white pellicle which falls as a whole on gentle 



FIG. 306. Cross-section of an olive twig at the level of a small tubercle;. 

 The open place is a bacterial cavity. Tumor composed chiefly of bark parenchyma, 

 the pith and wood cylinder being undisturbed. Result ot a pure-culture inocula- 

 tion using Bacterium savastanoi. Photographed in 1904. 



shaking. On steamed potato there is often a soluble brownish 

 stain (tawny or tawny- white). This stain also occurs in some 

 other media, i.e., water containing peptone and dextrose. 

 Potato starch is acted upon a little, the iodine reaction being 

 purple while that in the checks is blue. According to Petri, 

 potato starch is converted into amylodextrine and maltose. 

 The growth, except as influenced by the above-mentioned 

 brownish stain, is white on all media. Milk is gradually ren- 

 dered translucent (Compare with Nos. IV and XI). Lavender 

 or lilac-colored litmus milk becomes blue. No acid is ever 



