THE TOXICITY TO FUNGI OF VARIOUS OILS AND SALTS. 



19 



readily explained on the basis of chemical combination with the 

 media. 



The length of time required to make an initial growth on different 

 toxic media varies from a very few days up to seven weeks or more; 

 check cultures usually start within two or three days. Table I 

 illustrates this for a few preservatives. 



Table I. — Time required by Forties annosus on 0.2 per cent concentrations and F.pinicola 

 on 0.1 per cent concentrations to make initial growth from mycelium at 25 C. 



Preservative used. 



F. annosus. 



F. pinicola. 



Check cultures 



Sodium fluorid 



Coal-tar creosote 



Coal-tar creosote, Fraction II.. 

 Coal-tar creosote, Fraction III. 

 Coal-tar creosote, Fraction IV. 



Days. 

 2 to 3 

 20 



18 

 15 

 40 



Days. 

 2 to 2 



2-1 

 21 

 18 

 23 

 53 



It is thus seen tnat no growth demonstrable to the naked eye on 

 any of the concentrations mentioned occurred within a period of two 

 weeks, and the error which would occur in discontinuing the tests 

 at the end of 8 to 10 days, as several investigators have done, becomes 

 very evident. 



RECORD OF TESTS CONDUCTED. 



A description of each of the 18 preservatives used, accompanied 

 by individual tables and notes showing the rate, amplitude, and 

 appearance of growth on the different concentrations, as compared 

 with the check cultures, is given on the following pages. Under the 

 heading "Concentration of the preservative" in each table the average 

 radial distance to which the fungus has grown from the margin of the 

 transfer at the end of the test is indicated by numerals, 1 the position 

 of the first zero marking the killing point: Thus, 4 = 30 to 40 mm.; 

 3 = 20 to 30 mm. ; 2 = 10 to 20 mm. ; 1 = 1 to 10mm. ; = no growth. 



Sodium fluorid. 

 [Laboratory sample No. 1929. Purchased from Eimer & Amend, Chicago, 111.] 



Fungus. 



Tests. 



Times 

 killing 

 point 

 veri- 

 fied. 



Concentration of the preservative (per 

 cent). 





Number. 



Duration. 



0.05 



0.1 



0.15 



0.2 



0.25 



Cheek. 





9 

 11 



Weeks. 

 4 

 5 to 7 



1 j 4 

 1 3 



3 



2 



2 

 



1 







4 





4 

















1 It should be kept in mind that the growth rate designated as " 4 " is not necessarily the same on different 

 preservatives or different concentrations of the same preservative. All cultures which have produced 

 a growth of at least 30 to 40 mm. radius at the end of the test are included. Some of these may have reached 

 this point in two to three weeks, as in the case of the checks, while others may have required the full test 

 period; hence, the data as presented show only the relative retarding effect of the higher concentrations. 



