84 Journal of Agricultural Research voi. vi. no. 3 



of sheet filter paper were dissolved, the solution was diluted about 

 10 times with water, and the cellulose was precipitated with a 15 

 per cent solution of hydrochloric acid. After considerable dilution 

 the mixture was filtered, and the residue was washed repeatedly with 

 water to remove all copper and chlorin. This residue was added to an 

 agar medium consisting of agar, 10 gm. ; monopotassium phosphate, 

 I gm. ; magnesium sulphate, i gm.; sodium chlorid, i gm.; ammonium 

 sulphate, i gm.; calcium nitrate, 0.5 gm.; and the whole was made up 

 to 1 ,000 c. c. 



Poured plates of cellulose agar were made during May, inoculated with 

 Pseudomonas citri, Phoma sp., Gloeosporium sp., and Fusarium sp., and 

 incubated at room temperature. All grew poorly and none of the fungi 

 fruited on this medium. There was no evidence of the production of 

 cellulase except by Phoma sp. Within two weeks this organism had 

 formed clear translucent halos as shown in Plate IX, figure 5, indicating 

 that the cellulose had been hydrolyzed. Even though Phoma spp. 

 strongly dissolve paper cellulose, they may not behave in this manner 

 toward cell walls of Citrus spp., since other carbohydrates present would 

 be more readily available than cellulose. 



A further effort has been made to determine what other enzyms are 

 secreted by these organisms and what part they might consequently play 

 in the destruction of the tissues. Accordingly, Knop's mineral nutrient 

 solution was prepared for use as a stock solution. This stock solution 

 was then tubed and sterilized. To one set of these tubes of Knop's 

 solution starch was added, to another saccharose, and to another 

 maltose. They were then set aside and tested to determine whether 

 they were sterile. It had previously been determined that sterilization 

 subsequent to adding the carbohydrates resulted in a certain amount of 

 conversion of these carbohydrates. When it was determined that they 

 were sterile, four sets of four tubes each were taken of each of the nutrient 

 solutions. Three tubes in each set of four were inoculated with pure 

 cultures of one of the four organisms mentioned above and one tube in 

 each set was left as a check. After 10 days the solutions were tested, 

 with the following results : Fehling's solution showed a strong reduction 

 in the starch solutions in which Pseudomonas citri and Phoma sp. had 

 been grown, showing the production of diastase. There was no change 

 in the checks nor in the solutions in which the other organisms were 

 grown. 



Inversion of saccharose, as evidenced on the reduction of Fehling's 

 solution, had been accomplished in the solutions in which Phoma sp. and 

 Fusarium sp. had been grown, indicating the presence of invertase. 

 Positive tests for dextrose or glucose were secured with Barfoed's reagent 

 and with Nylander's reagent in these inverted saccharose solutions. 

 Negative results were secured with the other organisms and with the 

 checks. 



