Apr. lo. 1916 Citrus Canker 85 



Phoma sp. alone seemed to have any action on maltose. Inversion 

 into dextrose was shown by positive tests with Barfoed's reagent. 



Negative tests for lipase production were secured in the case of each of 

 the four organisms. 



From the foregoing tests it is seen that Phoma sp. secretes cellulase, 

 diastase, invertase, and maltase, and must therefore be regarded as very 

 destructive to the carbohydrate material of diseased tissues. Cellulase 

 very probably aids in the destruction of the cell walls ; diastase converts 

 the starch into maltose and dextrin and then further acts on the dextrin. 

 When a few drops of iodin were added to a starch solution in which 

 Phoma sp. had grown, blue and red colors developed, indicating amylo- 

 and erythro-dextrin. Maltase probably further reduces the maltose to 

 dextrose. 



It has also been found that Phoma sp. affects the acidity of the medium 

 upon which it is grown. This was determined by growth in pure culture 

 of the fungus on leaves and fruits of Citrus trifoliata. This material was 

 first macerated by passing it through a meat chopper. Thirty-gm. 

 samples of ground leaves and of fruits were then placed in 250 c. c. 

 Erlenmeyer flasks and were sterilized in an autoclave. After steriliza- 

 tion some were inoculated with Phoma sp. from pure cultures and others 

 left as checks. A copious white growth occurred on those which had 

 been inoculated. After a month 150 c. c. of distilled water were added 

 to each of the flask cultures and to the checks. The flasks were then 

 heated on a water bath for 30 minutes, the liquid filtered through asbes- 

 tos, and 25 c. c. of the filtrate taken for titration, using NI20 sodium 

 hydroxid, with litmus paper as an indicator. The following is repre- 

 sentative of the results obtained: 7.1 c. c. of NI20 sodium hydroxid 

 neutralized 25 c. c. of the filtrate from the leaves in the check flask and 

 9.8 c. c. that from the fruits in the check flask. The filtrate from the 

 leaves upon which Phoma sp. had been growing was neutral to litmus, 

 and that from the fruits required 1.3 c. c. of NI20 sodium hydroxid to 

 neutralize it. From this it is concluded that Phoma sp. is able to utilize 

 the organic acids as a source of food, a condition contrary to that which 

 Hawkins (7) found in a study of the chemical changes produced by the 

 brown-rot fungus on peaches. 



TAXONOMY OF THE FUNGUS 



An effort has been made definitely to assign this species of Phoma to 

 one of the numerous species of the form genera Phoma and Phyllosticta, 

 which have previously been described as occurring on parts of Citrus spp. 

 The pycnidia of the species under consideration are globose, ostiolate, 

 100 to 150A1 in diameter (PL XI, fig. 5, 6) and wholly or partially em- 

 bedded within the cankerous tissue. The pycnidial walls are thin, 

 being thickest around the ostiolum, and are very similar in color to the 

 corky brown host cells. The conidia are elliptical or oblong in outline. 



