29 



The followino- may he noted as some of the most characteristic pecu- 

 liarities of /^v. hyacinth I on gelatin culture media: 



(1) Liquefaction in neutral, acid, or alkaline gelatins, made with pep- 

 tone and l)eef broth containing muscle sugar, proceeds very slowly at 

 all temperatures (8^ to 32^ C), reaching out to the walls of the tube 

 long before it has involved the whole of the gelatin in stab cultures. 



(2) The addition of 5 or 10 per cent of cane sugar greatlv favors the 

 long-continued growth of the parasite and does not interfere with the 

 development of the 3"ellow pigment, but entirely prevents liquefaction, 

 or reduces it to an insignificant phenomenon easilv overlooked. 



(3) An extremely superficial, whitish, chemical tihii appeared after 

 some weeks around the surface growth, even when cane sugar was 

 added (see Nutrient Agars). 



(4) None of the gelatins showed any browning or other stain of 

 the substratum. 



(5) No gas bubbles appeared, except in one tube which turned out 

 to be contaminated. 



(6) Quite unlike strong growing facultative anaerobic species, such 

 as Bacillus coll or B. cloacce^ the stabs alwa3^s faded out gradually in 

 the depths, being best developed near the surface, and least in the 

 deeper parts of the gelatin. 



(7) The separate colonies, which in man}^ instances formed the 

 lower part of the stab, were always round or roundish, never spindle- 

 shaped, and were never distinctly 3^ellow, i. e., thej^ were white or 

 whitish, the free access of air appearing to be requisite for the devel- 

 opment of the bright ^^ellow pigment. 



(8) Even in Petri dish cultures the surface colonies developed better 

 than the buried ones, and the buried colonies in the surface la3^ers 

 grew better than those in the deeper parts of the gelatin. 



(9) Peptonized beef broth gelatin which is onh^ neutral or feebh^ 

 alkaline to litmus exerts a retarding influence on growth. The reac- 

 tion for best growth of this species lies somewhere between +15 and 

 of Fuller's scale. Litmus neutral gelatin also exerts a retarding 

 influence on several other plant parasites, e. g., Pseudommias cami^es- 

 tris and Bacillus amylovorus. 



NUTRIENT AGARS. 



(1) Streaks of Px. hyacinth) on brown agar No. 207 (+22) vielded a 

 good i)alc yellow growth and the same sort of crystals as cultures of 

 Ps. canipcstris^ viz, large compound X -shaped crystals of magnesium 

 ammonium phosphate.^ These crystals were, however, less abundant 

 than in cultures of Ps. campestris of the same age, and this was attrib- 

 uted to a feebler production of ammonia. The streak was still pale 3^el- 



' The composition of this agar is given iu Caitralblutt fur Baklerlologie, 2 Abt., Bd. 

 Ill, p. 480. 



