135 



leaves, a dendritic yeast, and a nondendritic yeast (both yeasts were 

 obtained from the sticky surface of Niagara grapes). In all of these 

 cases the gas soon foamed over the top of the test tube. An old 

 coconut culture of Px. hyacinth! also gave a very considerable quan- 

 tity of gas. 



The least amount of gas was obtained from adding HgO^ to 3-months- 

 old potato cultures of Jones' carrot rot bacillus. Three tubes were 

 tried, all of which behaved alike. At first there was no gas, then a 

 slow, long continued evolution of small bubbles, the total not l)eing 

 very great. A young potato culture of this bacillus (8 days old) 

 yielded gas almost from the start and in much greater quantity than 

 the old cultures. The reverse was true of Ps. campestris. A potato 

 culture ?> months old yielded gas more 

 promptly and in greater volume than did 

 a vigorous culture made from the same 

 tube and only S days old. Both, how- 

 ever, yielded nuich gas. On the con- 

 trary, even that from the young cultures 

 of Jones's bacillus fell far behind in 

 amount that which was evolved by the 

 other 10 bacteria and by the two yeasts. 

 Some gas was also obtained by pouring 

 H3O2 upon old rice cultures of various 

 funo'i, e. 2"., Fusarmm niveuri). F. vasin- 

 feet aril, Swingle's Atta fungus (culti- 

 vated by the writer from a nest of Atta, 



near Washington), and from an agar plate 



culture of cotton anthracnose. 



The yield of gas from the fungi named 



was insigniticant in comparison with that 



obtained from the yeasts and from the 



bacteria, exclusive of the old cultures of 



Jones's bacillus. The other bacilli and 



the two 3^easts gave so much gas that 



the tubes were tilled and frothed over, 



usually within a few minutes. 



In the accompanying illustration (fig. 2) a 3-months-old potato culture 



of Ph. pkmeoli to which H.,0., has been added is shown by the side of a 



check tube (uninoculated) to which H^Oj has also been added. In the 



one case there was a very copious evolution of gas bubbles, which 



tilled the tube; in the other there was only a very slight evolution of 



gas, which soon ceased. 



On heating a 3-months-old culture of Ph. phmeoU for 25 minutes at 



75 ' to 85^ C, and then adding the H,0.„ there was no evolution of gas 



Fig. 1. (a) Evolution of gas on add- 

 ing hydrogen peroxide to potato 

 culture of Ps. phamdi: (b) Unin- 

 oculate<l lulie, to which hydrogen 

 peroxide has just been added. 



