[Vol. 9 



366 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



From table in there is a slight suggestion that acetate and 

 phosphate ions are markedly injurious to growth, while malate 

 and tartrate ions exercise a very retarding influence; in contrast 

 to these the citrate, chloride, and lactate ions have no marked ef- 

 fect. It should be noted that there was no growth in any of the 

 acids tried at the end of 24 hours although neutral broth kept at 

 the same temperature, 25° C, showed marked clouding at the end 

 of that period. This is to be expected since this organism in nu- 

 trient broth grows best around the neutral point, between Ph 6 



and Pn 8. It is rather surprising to see the phosphate act as a 

 poison and this perhaps needs to be repeated before accepting the 

 result although the work was done carefully and carried out in 

 triplicate. More will be said of this later. As far as the acetate 

 is concerned the result obtained substantiates the findings of 

 others (see, for example, Wolf and Shunk [II, '21, pp. 14-20]). 



TABLE IV 

 CHANGE IN P H AFTER 10 DAYS GROWTH IN ACID BROTHS 



Original Ph Final Ph 



. — ■ — ^^^— i »■■■■■■■ — ■■ 



Citric acid 4.9 7.4 



Hydrochloric acid 5.5 7.4 



Lact ic acid 5.3 6.8 



Malic acid 5.0 6.8 



Table iv is of interest not only because it shows the produc 

 )n of alkali in this medium, a marked character of this organ 



ism. but also b 



a given period of 



nal hydrogen-ion concentration is not necessarily the same 

 though the initial concentration may have been quite simi- 



there 



alkalinity 



Why lactic acid should produce a higher final hydrogen-ion con- 

 centration than citric acid is a question; perhaps this is due to a 

 difference in the dissociation of salts formed, but in the case of 

 malic acid this is doubtless coupled with a lower amount of 

 growth in the same time period (see table in). 



It has already been noted that media will change on standing 

 and that changes may be due to glassware or to some rearrange- 

 ment in the chemical make-up of the medium. The changes as 

 noted in table v are not very great; yet in some of these it is 

 such that if the hydrogen-ion concentration were the only limit- 

 ing factor the organism ought to grow in the changed medium. 



