86 



were present, and a feeble brown stain, thought to have been 

 detected on the fifty-fourth day, was not well enough developed to be 

 recorded as certainly present. On this date there was more than twice 

 as much precipitate as in the corresponding tube of J^s. catnpestris. 

 This dextrin had been ten times precipitated with alcohol in the 

 Division of Chemistry, United States Department of Agriculture. It 

 gave a heavy yellowish precipitate on boiling 1 minute in Soxhlet's 

 solution, ])ut no precipitate on boiling 2 minutes in Barfoed's reagent. 



(4) In distilled water (10 c. c. in tubes of resistant glass) containing 

 4 per cent of Witte's peptonum siccum and 4 per cent of maltose 

 there was no retardation of growth, and for the first week or so the 

 culture closely resembled the preceding. On the twelfth day the fluid 

 was distinctly alkaline to litmus, but it was less cloudy than the pre- 

 ceding and there was far less precipitate. On the twenty -ninth da}" 

 the fluid was plainly and rather strongly alkaline, but there wa; only 

 about one-tenth as much precipitate as in the tube containing the 

 dextrin. On the fortieth day the fluid was still cloud}-, but was not 

 browned. The rim was not very aljundant and was paler than in the 

 preceding. The precipitate was the same shade of pale yellow as in 

 the tube containing the dextrin, but there was only one-tenth to one- 

 fifteenth as much. On the sixty-fifth day the fluid was strongly 

 alkaline, but both in this and in the preceding the blue color soon 

 disappeared from the neutral litnuis paper, leaving it redder than 

 before. No crystals were formed. 



In the corresponding tube of Ps. canipestris there was a distinct 

 browning of the fluid, which was first noticed on the fortieth day. 

 Ps. p]i((f<eoli browned neither fluid. 



Crude Vegetabi.e Substances. 



The behavior of Ph. hyacinthi in contact with steam sterilized solids 

 and fluids derived from plants has been discussed so fully under 

 Sensitiveness to acids and Growth on solid media that it is only neces- 

 sar}'^ here to recapitulate a few of the more important discoveries. 



(1) All my observations tend to show that plant acids, even in 

 comparativel}' small doses, prevent growth, and that still smaller 

 quantities retard growth. It is, therefore, probable that these acids 

 do not serve directly as food. Certainly the behavior of this organism 

 in nutrient fluids containing malic acid is extremely unlike that of 

 organisms which are believed to use this acid as a food, e. g. Bacillus 

 amylovortis. 



(2) Starch, as we have seen, is transformed into substances which 

 can be assimilated onl}^ with the greatest difliculty. 



(3) Growth on steamed vegetables poor in sugar was always rather 

 meager. Substrata containing rather more sugar gave a correspond- 

 ingly better growth. 



