i66 



BACTERIA IN RELATION TO PLANT DISEASES. 



In addition to large quantities of carbon dioxide, ginger beer contains during eaily stages of 

 fermentation traces of alcohol and acetic acid, while relatively large quantities of an acid resembling 

 lactic acid, if not identical with it are formed. 



Just what each organism gains from the combination was not made out clearly, but the yeast 

 seems to do better in the presence of the bacterium than where separated from it. 



The following pertinent paragraphs from Ward's paper may close this review: 



"Everything points to the view that the relations between the yeast and the bacterium are those 

 of true symbiosis, because every attempt to feed the schizomycete with dead yeast-cells or decoctions 

 of such, or detect it embracing such cells in a dead or feeble condition has failed. 



" It is significant that the synthesis of this dual organsim — which is so strikingly like the lichen 

 that we may compare it forthwith with one of the gelatinous forms — was most easily brought about 

 by adding the yeast-cells to already advanced cultures of the bacterium, both having been grown 

 in the same medium and under like conditions. * * * 



"The schizomycete is favored by obtaining some substance or substances directly they leave 

 the sphere of metabolic activity of the yeast-cells ; it can benefit by the presence of these substances, 

 even apart from the living yeast, though to a less extent. 



"The yeast, on the other hand, benefits by these substances being removed and destroyed, hence 

 its renewed and continued activity — as evidenced by the steady and copious evolution of carbon- 

 dioxide for weeks, and the corresponding increase of the yeast-cells by budding — when the symbiosis 

 is established. 



"For the present this can only be regarded as a hypothesis. It might be objected that I have 



inverted the order of things — that, since the schizomycete is 

 able to evolve small quantities of carbon dioxide daily from 

 saccharine solutions, it may be that its powers are enhanced 

 by the yeast removing inhibiting substances of its activity. 

 The objection is possibly valid, but I think the former hypo- 

 thesis explains most of the facts : How, for instance, is it to be 

 explained that the schizomycete slowly and steadily converts 

 the whole of the liquid sugar-solution into a solid gelatinous 

 mass, if the organism excretes such inhibiting substances?" 





THE SO-CALLED BEER-SEED. 



Fig. 45.' 



The writer has had but one opportunity of seeing 

 kefir-like grains. These were sent from Alissouri to the 

 .%'^'^^^MkJ»'£J'^ Department of Agriculture under the name of "Califor- 



nia Beer-seed." They were acid to litmus paper, and 

 had a feebly acid, rather agreeable, ester-like odor. The 

 roundish gelatinous granules (fig. 45) consisted of several 

 kinds of bacteria, and of one or more kinds of yeasts, together with oblong, large, jointed 

 threads which stained like yeast and were interpreted as Oidiuni laclis. The majority of 

 the yeast-cells were round or roundish and the long oval or elliptical ones appeared to be of 

 a different sort. Morphologically there appeared to be at least three kinds of bacteria in 

 the grains, but no coccus forms were detected. Quite unlike the kefir figured by Beyerinck, 

 the yeast-cells were not in a uniform thin layer on the surface, but were distributed through 

 the grains in little clumps, most of the clumps, however, being in the outer parts of the 

 grains (fig. 46). The greater portion of the bacterial mass consisted of rather thick short 

 threads. Long filaments were exceptional. The appearance of the more common yeast 

 and schizomycete as crushed out in water is shown in figure 47. The general relation of 

 yeasts and bacteria in the substance as determined by thin sections of fresh grains and by 

 microtome sections of embedded material is shown in fig. 48. The writer did not observe 

 any bacterial forms corresponding to the end-splitting ones figured and described by Mar- 

 shall Ward, but prolonged study was not given to the subject. 



Poured-plates made from the granules on ordinary +15 beef-bouillon agar yielded a 

 considerable number of small, .slow-growing white colonies which proved to be a yeast. 



*FiG. 45. — Grain.s of "California bccr-sccd." Received in 1508 from Missouri. 



