CULTURAL CHARACTERS OF CHESTNUT-BLIGHT FUNGUS. 7 



MOISTUHE TESTS. 



Three series of several flasks each on corn meal were made with dif- 

 ferent quantities of water, using Endothia radicalis and E. parasitica, 

 as follows: 



Series 1. — Com meal. 10 grams, plus water, 10 cubic centimeters. 

 Series 2. — Com meal, 10 grams, plus water, 15 cubic centimeters. 

 Series 3. — Com meal, 10 grams, plus water, 20 cubic centimeters. 



The two species grew equally well in each series. There was, how- 

 ever, a marked difference as to the time of appearance of spores in the 

 different series. Spore production began at about the same time 

 with both species in the same series. 



At the end of two weeks in series 1, Endothia parasitica showed 

 numerous small spore pustules. E. radicalis at the same age showed 

 but four pustules in each flask. These pustules were much larger 

 than those of E. parasitica. In series 2 both species showed an inter- 

 mediate condition of development. In series 3 E.parasitica developed 

 somewhat more mycelium than in series 1, and there were only a few 

 scattered spore pustules. E. radicalis produced more mycelium than 

 in series 1 and only two or three very small pustules. 



At the end of two months in series 1 Endothia parasitica had cov- 

 ered the entire surface with small confluent spore masses. E. 

 radicalis now showed numerous large pustules with extruding spore 

 masses. Series 2 was intermediate, as before. In series 3 E. para- 

 sitica showed a large number of separate small spore pustules with 

 white mycelium between them, while E. radicalis showed but few 

 stromata, much enlarged and extruding large spore masses. 



It will be noted that the greatest spore production occurred in the 

 cultures having the least quantity of water added. 



TEMPERATURE TESTS. 



Fulton * found that conidia germinate best at a temperature of 60° 

 F. (15.5° C.) and distinctly less rapidly at 10 degrees above or below 

 the optimum. Ascospores germinate best at a temperature of about 

 70° F., but give a good percentage of germination at 85° and 45° F. 

 He also found that early growth is most rapid at the optimum 

 temperature for germination. 



A few experiments have been made by the writers to determine 

 the temperature relations of the organisms. 



Series 1 (six tubes of each) on potato agar + 7. — At the end of 14 

 days the cultures kept at 40° C. showed no growth in an}- case. 



At 35° C. Endothia parasitica showed a small amount of an irregular 

 rough leathery growth, orange next to the agar. E. radicalis showed 



1 Fulton, H. R. Op. cit. 

 [Cir. 131] 



