CHESTNUT BARK DISEASE. 433 



4 per cent, tannic acid, the growth of the fungi tends to form 

 a more or less firm coating over the surface, after the manner 

 of growth on the solid medium. Above 4 per cent, the growth 

 becomes gradually less evident, generally showing in floating 

 patches, embedded masses, or lateral growths around the side 

 of the glass. Finally, at the highest percentages, 10 to 14, growth 

 entirely ceases, only one having been successful at the latter 

 strength in any of the tubes. 



(5) In the higher percentages of tannic acid E. gyrosa shows 

 an enfeebled growth sooner than does var. parasitica, since at 

 6 to 8 per cent, it makes comparatively little growth, correspond- 

 ing to that made by the variety at about 10 per cent. It gen- 

 erally fails entirely to make any growth at above 10 per cent., 

 or only a poor growth above 8 per cent, in most of the tubes; 

 while the variety in only one case made any growth above 12 per 

 cent, and rarely any but a poor growth above 10 per cent. 



(6) At the higher percentages the difference in the appear- 

 ance of the two fungi is less marked than at the lower, so that 

 from 4 per cent, up, where spore production of the variety is 

 largely cut out, they are scarcely to be distinguished. 



(7) There was some variation in development with the dif- 

 ferent cultures of the same fungus in the higher percentages of 

 the tannic acid, as shown by one of the cultures of var. par- 

 asitica from Connecticut which had been in artificial culture for 

 over three years failing to grow quite as well as the more recent 

 cultures. These variations are perhaps not constant. 



(8) All the preceding notes relate to cultures that were inoc- 

 ulated from plain potato- juice agar directly onto those contain- 

 ing various percentages of tannic acid. Another set of cultures 

 was made in which each was brought up gradually through all 

 the lower percentages of tannic acid. In these it was found that 

 this gradual acclimatization to the tannic acid gave a somewhat 

 more luxuriant growth of both fungi at the higher percentages 

 than when transferred directly from the potato- juice agar to 

 these. 



Later experiments based on the preceding results were made 

 with all our cultures of E. gyrosa (26 in number) and those of 

 var. parasitica (22 in number), using two cultures of each and 

 the following percentages of tannic acid: 4.0, 6.0, 8.0, 10.0. 

 These cultures showed, as in the previous tests, that the variety 



