FusARiA OF Potatoes 259 



dark, depressed area of dry rot at the stem end of the tubers, with cream- 

 white, dense tufts of conidiophores, up to 1 centimeter high and powdered 

 with conidia. (For microscopic characters see figure 47.) Pure cultures 

 of this organism were obtained both from the aerial conidia and from 

 plantings of the rotted tissues of the tubers. 



The organisms in general differ much from F. striatum, but in certain 

 cultures (in sporodochia-producing stage on whole steamed potato tubers) 

 resemble it very closely. 



Measurements of conidia on different media are as follows: 



On potato tuber plug, culture eighty-two days old: 



(1) Conidia from aerial mycelium 



Conidia: 0-septate, 95 per cent, 8x3 (6-15 x 2.1-4)/^ 



1-septate, 5 per cent, 15 x 4 (13-21 x 3.4-4.4) /x 

 3-septate, rare 



(2) Chlamydospores, intercalary and terminal, unicellular and in chains 



0-septate, 9.8 x 8.7 (5.2-16 x 5.2-12) ^ 



On hard lima-bean agar with 2 per cent glucose, culture sixty-four 

 days old: 



(1) Conidia from aerial mycelium close to substratum 

 Conidia: 0-septate, 80 per cent | 



1-septate, 17 per cent > (size same as above) 

 2-septate, 2 per cent J 



3-septate, 1 per cent, 33 x 4.8 (22-41 x 4.3-5.2) jn 

 4-septate, rare, 45 x 4.8 (only a few measured) 



(2) Chlamydospores 



0-septate, 9.5 x 8.8 (6.1-12 x 5.2-ll);u 

 1-septate, 18 x 10 (16-22 x 5-12) m 



On hard lima-bean agar, culture twelve days old: 



(1) Conidia from aerial mycelium 

 Conidia: 0-septate, 60 per cent 



1-septate, 30 per cent 



2-septate, 1 per cent 



3-septate, 6 per cent, 37 x 4.5 (28-48 x 4-5.3) m 



4-septate, 3 per cent, 43.6 x 5 (40-49 x 4.3-5.2) /z 



5-septate, rare, size about that of 4-septate 



(2) Chlamydospores, mostly 0-septate, 9 x 8.7/i 



