135 



leaves, a dendritic yeast, and a nondendritie yt^ist (both yeasts were 

 obtained from the stieky surt'aee of Niagara grapes). In all of these 

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

 coconut culture of Ps. /n/ar/iif/i/ also gave a very ('onsidera))le ({uan 

 tity of gas. 



The least amount of gas was obtained from adding HgOg to S-montiis- 

 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 being- 

 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 8 months old yielded gas more 

 promptl}^ and in greater volume than did 

 a vigorous culture made from the same 

 tube and onh^ 8 da3^s old. Both, how- 

 ever, 3'ielded 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 b}^ the two yeasts. 



Some gas was also obtained by pouring 

 HgO., upon old rice cultures of various 

 fungi, e. g. , Fusariimi niveimi^ F. vasin- 

 fectiuit^ 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 insignificant 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 yeasts gave so nmch gas that 

 the tubes were filled and frothed over, 

 usually within a few minutes. 



In the accompanying illustration (fig. 2) a 8-months-old potato culture 

 of Ps. pJutseoli to which H^O.^ has been added is shown by the side of a 

 check tube (un inoculated) to which H^O.^ has also been added. In the 

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

 filled the tube; in the other there Avas only a very slight evolution of 

 gas, which soon ceased. 



On heating a 8-months-old culture of /^v. jthascoli for -io mimites at 

 75"^ to 85^^ C, and then adding the HoO.^, there was no evolution of gas 



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

 ing hydrogen peroxide to potato 

 culture of Ps. phaseoli; (6) Unin- 

 oculated tube, to which hydrogen 

 peroxide has just been added. 



