1923] 



CAMP — CITRIC ACID AS A SOURCE OF CARBON 241 



doubtedly an important one in the rotting of citrus fruits. The 

 examination of a considerable amount of decayed fruit in ship- 

 ments from Florida and California indicated that this fungus 

 may not be as common in the winter as at other times, and that 

 there are other fungi of this group with blue-green or green 

 spores which may be at times mistaken for it. The organisms 

 used in the work are reported upon below: 



Penicillium stoloniferum Thorn. — This fungus was sent by 

 Dr. Fawcett of the Citrus Experiment Station of California. 

 It had been isolated from rotting citrus fruit and was thought 

 to be P. digitatum at the time, but it was later identified by Dr. 

 Thorn as P. stoloniferum. The habitat given by Thorn ('10) is 

 decaying Polypores and Boleti, but the fungus was found by the 

 writer on decaying masses of citrus fruits. The culture was 

 found infective to a certain degree, and it readily attacked lemons 

 or oranges which had been partially rotted by other fungi. It 

 probably does not constitute a primary agent in the infection of 

 these fruits under ordinary conditions, but is of secondary import- 

 ance, bringing about a final destructive rot. It grew well on 

 most synthetic media, tolerated high acidity, used citric acid 

 readily, and usually produced an alkaline reaction in the medium. 

 The spores are considerably smaller than those of P. digitatum 

 and the spore masses do not have the same olive-green color. 



Penicillium sp. — This fungus together with the one just dis- 

 cussed, was sent to Dr. Thorn, for it had been thought that this 

 might be P. italicum, although the spores were considerably 

 smaller than those described for that fungus. Dr. Thorn stated 

 that it was not related to P. italicum and that he could not name 

 it definitely. Its growth on most media was blue-green to gray 

 and very vigorous. It grew well on synthetic media, used citric 

 acid readily, and usually produced an alkaline reaction in the 

 culture medium. In general its reactions were very similar to 

 those of P. stoloniferum. 



Penicillium digitatum Sacc. — This fungus is well known as the 

 cause of a destructive rot of lemons often seen in the market. 

 It was a poor organism for cultural work since it did not grow 

 well unless peptone was supplied as a source of nitrogen. It 

 used citric acid, but in a fermentative way, since there was no 



