29 



The following may be noted as some of the most characteristic pecu- 

 liarities of Px. kyac'mtkl on gelatin culture media: 



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

 tone and beef 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 greatl}^ favors the 

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

 development of the yellow pigment, but entirel}^ prevents liquefaction, 

 or reduces it to an insignificant phenomenon easily overlooked. 



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

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

 added (see Nutrient Agars). 



(4) None of the gelatins showed any brownmg 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. cloaccB^ the stabs always 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 many instances formed the 

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

 shaped, and were never distinctly 3'ellow, i. e., the}^ were white or 

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

 opment of the bright 3'cllow pigment. 



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

 than the buried ones, and the buried colonies in the surface layers 

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



(9) Peptonized beef broth gelatin which is only neutral or feebly 

 alkaline to litnms 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., Pseudomonas cwm^es- 

 triH and Bacdhim amylovorus. 



NUTKIENT ACiAKS. 



(1) Streaks of Ps. %(7(?/w/A/ on brown agar No. 207 (-f 22) yielded a 

 good pale yiOlow growth and the same sort of crystals as cultures of 

 /^•. ca/nj)r.sfrl.s^ viz, large compound X -shaped crystals of magnesium 

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

 than in cultures of Z^-. cavijicHtris of the same age, and this was attrib- 

 uted to a feel)ler production of ammonia. The streak was still pale yel- 



'The composition of this agar is givt'ii in Cmtralbkitt fur Baklerlologie, 2 Abt., Bd. 

 Ill, p. 480. 



