42 



to render the fluid yellowish, Ps. hyacinth i did not redden the fluid, but 

 made it colorless, the bacterial precipitate becoming rosy or salmon- 

 colored. Produces indol slowly in peptonized beef broth and in pep- 

 tonized Uschinsky's solution; does not produce nitrites in these 

 solutions. Does not reduce potassium nitrate to nitrite in peptonized 

 beef bouillon. Not a strong-smelling germ. Not readily destroyed 

 bj^ its own decomposition products except in media containing alcohol. 

 Will not grow in the thermostat at 37° C, and grows verj- feebly on 

 some media and not at all on others at 34° to 35° C. Optimum tem- 

 perature 28° to 30° C. , or thereabouts. Minimum temperature approx- 

 imately 4° C. Thermal death point (10 minutes' exposure) 47.50° 

 C. ; nearly all the rods are killed at 47° and a great many at 46.50° C. 



Did not grow at room temperatures after 6 days 

 exjDOSure in alkaline beef broth in the thermo- 

 stat at 35° to 36.35°. Does not grow well in 

 Uschinsky's solution. Grows much better in 

 Uschinsky's solution when j)eptone is added to 

 it. Grows well with a bright yellow color on 

 cylinders of steamed coconut flesh, standing 

 with one end in distilled water. 



Pathogenic to hyacinths. Enters the plant 

 through wounds, through the blossoms, etc., and 

 multiplies in the vascular system, filling the ves- 

 sels, especially those of the bulb, with a bright 

 yellow slime consisting of bacteria. The walls 

 of the vessels are destroyed and extensive cavi- 

 ties are formed in the bundles. The parenchyma 

 around the bundles is also involved, but only 

 very slowlj-, the organism being a feeble de- 

 stroyer of cell walls. The host plant is not 

 rapidly destroyed, a year or more being neces- 

 sary. The cells are first separated by solution 

 of the middle lamella, but the wall itself seems 

 to finally disappear. The cavities contain innu- 

 merable bacteria mingled with fragments of the dissolved bundles and 

 of the surrounding parenchyma. 



First described by Dr. J. H. Wakker from the Netherlands, where 

 it often causes serious losses in the hyacinth gardens. Not known to 

 occur in any other part of the world. 



Feb. 10 



JMar.l4 



.Apr. 12 



Fig. 6.— Ps. hi/acinthi grow- 

 ing in strongly alkaline 

 (0) gelatin with 10 per 

 cent cane sugar. No lique- 

 faction. The surface 

 curves are due to the very- 

 gradual drying out of the 

 gelatin. 



REMARKS ON RELATIONSHIP. 



CloseU" related to Ps. campestris (parasitic on Cruciferous plants), 

 Ps. phaseoU (parasitic on beans), and less so to Ps. stewarti (parasitic 

 (?) on corn, especially sweet corn). Readily distinguished from the 

 two organisms first named by (1) its brighter color; (2) its lower 

 thermal death point; (3) its manner of growth on potato cylinders 



