ENDOTHIA PARASITICA AND RELATED SPECIES. 47 



rate of growth might be due. at least partly, to more rapid drying of 

 the agar at 31° C, or possibly to the more rapid development 

 of some toxin, as was suggested by Balls (7) to explain a similar 

 observation on the " soreshin " fungus. These observations threw 

 doubt upon the accuracy of the writers' previous conclusions, and 

 made it seem possible that the optimum temperature of the species 

 of Endothia might be well above room temperature. This could only 

 be determined accurately by some method which would control tem- 

 perature without altering the supply of moisture. Some months 

 after the above tests were concluded it was discovered that the various 

 species of Endothia would grow readily on several liquid media. 

 Consequently, several series of tests on liquid media were run parallel 

 to those described above, except that the tests were continued for 

 only four days. Experiment showed that at the higher temperatures 

 the medium became considerably reduced by evaporation if left for 

 a longer period. 



TESTS ON LIQUID MEDIA. 



In the series of tests on liquid media, all the species of which cul- 

 tures had been obtained were grown on Cook's medium (see p. 41) 

 both in tubes and in flasks, using ten tubes and six flasks at each 

 temperature. The cultures of Endothia gyrosa and E. singularis 

 were made with bits of mycelium from pure cultures. The other 

 species were grown from conidia and the cultures were kept for two 

 days at room temperature, in order to allow the conidia to germinate 

 before being placed in the temperatures to be tested. 



The following temperatures were used for making the tests: 40°, 

 37.5°, 35°, 29°, and 27°, and room temperature which was fairly 

 constant at about 22°, 17°, 12°, 9°, 7°, 3°, and 2° C. There was some 

 variation in the temperature of the incubators and refrigerators 

 used, but in most cases they did not vary more than 1 degree above 

 or below the temperature indicated. At 40° there were occasional 

 traces of growth, especially in Endothia parasitica, but this may have 

 occurred when the incubator dropped to 39° C. There is no regular 

 and continued growth at this temperature. 



At 37.5° C. there was perceptible growth in all the species. This 

 is in striking contrast to the results on solid media, as no species 

 grew at a temperature above 35° C. on solid media. 



At 35° C. Endothia parasitica showed practically the same amount 

 of growth as at 27° and 29° C. for the first three days, but fell behind 

 after that. E. flue?is showed less growth at 35° than at the lower 

 temperatures. These two species were the only ones tested at 35° C. 



At 27° and 29° C. growth was markedly more abundant than at 

 37.5°, and in most of the species was more abundant than at room 

 temperature. In Endothia gyrosa and E. flu#ns mississippiensis the 



