1919] 



SCHMITZ STUDIES IN THE DECAY OF WOOD 



115 



TABLE XIII 



RATE OF GROWTH OF FOMES PINICOLA, POLYSTICTUS VERSICOLOR, AND LENZITES 



SAEPIARIA ON MEDIA OF INCREASING ACIDITY 







Diameter of colonies 



i in centimeters 





Reaction ot 















media, Fuller's 



scale 



Fomes 



pinicola 



Polystictus versicolor 



Lenzites saepiaria 



6 days 



1 8 days 



6 days 



8 days 



6 days 



8 days 



+ 2.5 



No growth 



1.8 



No growth 



1.6 



No growth 



2.3 



+ 4.5 



1.8 



3.0 



4.9 



7.0 



2.3 



3.7 



+ 6.0 



1.9 



3.1 



5.4 



7.6 



2.4 



3.9 



+ 7.75 



2.0 



3.1 



6.3 



8.3 



2.4 



3.9 



+ 9.75 



1.9 



3.1 



6.6 



9.3 



3.2 



4.1 



+ 13.5 



2.1 



3.3 



5.7 



7.4 



2.4 



4.0 



+ 14.0 



1.9 



3.1 



5.8 



7.4 



2.5 



4.0 



+ 16.25 



1.8 



2.9 



5.3 



6 9 



2.6 



3.9 



+ 18.5 



1.7 



2.9 



5.1 



6.4 



2.7 



4.1 



+21.25 



1.8 



3.0 



4.7 



6.0 



2.5 



3.9 



+22.25 



1.6 



3.0 



4.4 



5.7 



2.3 



3.3 



+24.5 



1.7 



3.0 



4.3 



4.6 



2.1 



2.8 



There is but little difference in the rate of growth of Fomes 

 )la on media ranging from + 5 to + 24.5 acid, Fuller's 

 On a medium of + 2.5 there is a decided retardation 



scale. 



in the rate of growth. Polystictus versicolor shows a marked 

 response to the reaction of the medium. A maximum is at- 

 tained when the medium titrates -f 9.75, Fuller's scale, with a 

 steady decrease in the rate of growth as the acidity increases. 

 The effect of the reaction of the medium on the rate of growth 

 of Lenzites saepiaria is quite similar to that on Fomes pinicola 

 except that there is a marked retardation on the media of the 

 higher concentrations. 



It is appreciated that by titrating samples of acidified agar 

 in this manner the actual acidity of the medium is not defi- 

 nitely determined, due to the buffer effect of the agar on the 

 hydrogen ions ; yet the results would indicate that slight varia- 

 tions in the reaction of the substratum would have little or no 

 effect on the rate of development of Fomes pinicola or Lenzites 



saepiaria but that they might have in the case of Polystictus 

 versicolor. 



CULTURE RELATIONS: BACTERIA 



The bacteria used were chosen, with one exception, with ref- 

 erence to their acid or alkaline reactions on culture media. The 

 presence of a nitrogen-fixing soil form was also tried. The 



