46 



55 day^ the 3-ellow slime on the aerial part of the cylinder and the 

 fluid in the bottom of this tube were both acid. There was no trace 

 of any alkaline reaction, but this acidity was feeble, i. e.. not much, 

 if any, more pronounced than in the dried-out juice of the check 

 tubes. On the thirtieth day. in another tul^e of the same series, a 

 mass of germs from the top of the cylinder reacted feebly acid, or at 

 least there was no alkaline reaction on neutral litmus paper. After 

 55 days a large loop of yellow slime from the same tube showed no 

 alkaline reaction when rubbed on neutral litmus paper, not even 

 when stirred up in a drop of distilled water. At the same time no 

 acid reaction could be detected. The slime was neutral. 



No brown stain appeared in any of these cultures (67 days). 



See also Feeble diastasic action and Relative nutrient value of carbon 

 compounds for additional notes on growth on solid media. 



SP:NSITrV'ENESS TO ACIDS. 



The failure of P.s. Jiyachnhi to produce any immediate symptoms, 

 even when inserted into the h^^acinth-leaf parenchyma by the million, 

 the slow progress of the disease when it finally appeared, and the 

 extent to Avhich growth is restricted to the immediate vicinity of the 

 vascular bundles, have been described in Bulletin Xo. 26. This behavior 

 of the organism in the host plant, which resembles that of Ps. cam- 

 pestris in the turnip and cabbage, led me to suspect it might be very 

 sensitive to acids. To test this supposition the following experiments 

 were made: 



Acid Beef Broths. 



In all cases the rate of growth in beef broth made neutral to phenol- 

 phthalein was assumed as the standard. 



(1) The first trials were with stocks 286a. 286b, and 286d. Stock 

 286a was a 1 : 2 beef broth, to which no sodium chloride or alkali was 

 added, and the acidity of which was 4-25 of Fuller's scale. Stock 

 286b was a portion of the same broth rendered neutral to phenol- 

 phthalein (U of Fuller's scale), by caustic soda. Stock 286d was a por- 

 tion of 286a boiled down so that it was quite yellow and strongly acid, 

 i. e., -1-80 of Fuller's scale. Each tube contained 10 c. c. of broth. 

 All were inoculated at the same time from an alkaline beef-broth cul- 

 ture tt days old, and were kept together in feeble light, at room tem- 

 peratureJ of 20- to 24° C. 



Bt'Sult. — The alkaline broth (2S6b) clouded in 26 to 72 hours, accord- 

 ing as the infection was made with a large loop or with a tiny drop 

 from the tip of a platinum needle. Stock 286a (feebly acid) clouded 

 in 48 to 168 hours, according to manner of infection (l(M)p or needle). 

 Stock 286d, whichever way inoculated, remained clear until the close 

 of the experiment (49 days). 



