326 BACTERIA IN RELATION TO PLANT DISEASES. 



Results.- There has been two or three times as much growth in tubes to which the potassium 

 nitrate was added, but it is not a good growth, i. e., such as would take place in bouillon with peptone. 

 Tests made some days ago, i. e., after a distinct difference developed, showed no nitrite present in 

 inoculated tubes containing the potassium nitrate, so the puzzle is where the bacterium obtains its 

 necessary nitrogen. Perhaps under stress it is able to assimilate N. slowly from unsuitable material 

 just as Bad. hyacinthi under similar conditions is able to take C. from potato-starch. On July 16, 

 for comparison, inoculations were made in Fischer's mineral solution plus i per cent cane-sugar 

 and i per cent Witte's peptone. These tubes although they have not been inoculated as long as the 

 ones containing potassium nitrate have given twenty times as much growth (clouding and yellow 

 precipitate) . 



Further tests were made in February, 1911, as follows: To Fischer's nutrient mineral 

 solution i per cent nitrate of potash was added. The strained solution was then divided 

 into two equal portions. To one half was added i per cent cane-sugar and to the other 

 i per cent glycerin. Inoculations were made from young bouillon cultures, and for checks 

 on the amount of growth additional inoculations were made into our ordinary + 15 pepton- 

 ized beef bouillon. Two strains of the organism were used, one isolated in my laboratory, 

 the other received from Harding of Geneva, N. Y. The results after 26 days were as follows : 



(1) N. Y. strain in Fischer's nutrient mineral solution with cane-sugar and potassium nitrate: 

 Fluid clear, moderate pale yellow precipitate and interrupted white pellicle shaking down easily 

 into small fragments which make the fluid very flocculent. Five tubes : About \ as much growth as 

 in the check-tubes in peptone beef bouillon which have a yellow rim and a copious yellow pellicle. 



(2) Washington strain in the same: Less growth, scanty pale rim, no pellicle. Scanty yellow 

 precipitate, no flocculence on shaking, but a moderate clouding. Five tubes: About as much 

 growth as in the checks in the peptone bouillon. 



(3) N. Y. strain in Fischer's solution with Schering's c. p. glycerin and potassium nitrate: 

 A" distinct growth but less pellicle and less precipitate than in i. A thin rim with no distinct color. 

 Fluid well clouded on shaking with numerous small flocculent masses. Five tubes : About one-tenth 

 as much growth as in the peptone bouillon checks. 



(4) Washington strain in same: Like 3 but more thinly clouded. Yellow precipitate. Five 

 tubes: About one-fifteenth as much growth as with checks. Each tube was tested with boiled starch 

 water, i :2oo potassium iodide water and a few drops of sulphuric acid water. No blue reaction 

 took place. 



I can not think, therefore, that this organism is a nitrobacterium in Dr. Fischer's 

 sense of the word, since it does not reduce nitrates to nitrites, so far as can be determined 

 by the test with starch, potassium iodide, and sulphuric acid, and obtains its nitrogen much 

 more readily from peptone than from KNO 3 . It can use glycerine in presence of KNO 3 . 



Hecke isolated this bacterium in the winter and in spring from frozen kohlrabi. The 

 organism probably winters over in the soil, but up to this time no one has actually plated 

 it out of soils. In Smith and Swingle's experiments ten freezings and thawings in course 

 of about 6 hours did not destroy all of the individuals in a bouillon culture, but the first 

 two or three freezings destroyed most of them. 



In experiments made some years ago, the writer found this organism much more re- 

 sistant to dry air than Harding's first report would indicate, to-wit, in Harding's experi- 

 ments invariably destroyed in 45 hours, and 7 out of 8 cover-slips sterile at the end of 2 1 

 hours. In my own tests the organism on 8 out of 24 cover-slips was alive after 34 days when 

 inoculated from a potato-culture 2 days old, and on 2 out of 23 cover-slips when inoculated 

 from bouillon. On agar the writer found the organism very resistant, to-wit, alive after 

 17! months. Much seems to depend on the thinness of the layer and the nature of the 

 surface on which it is dried. Recently Harding and his associates have shown that when 

 placed on cabbage seed and set away in test tubes, sealed and unsealed, a certain number 

 of the bacteria were still living at the end of a year. 



Harding tested resistance to disinfectants by adding one drop of a freshly clouded 

 bouillon-culture to 10 cc. of the substance and making bouillon sub-cultures therefrom at 



