MICHIGAN ACADEMY OF SCIENCE. 99 



Avere as ineffective as had beeu supposed by most writers. Other 

 fungicides were also tested in tlie hope of finding sonietliing which 

 would prove effective. Frank's work was also duplicated in an 

 attempt to see if the immersion of spores in the spray really was 

 as harmless as had been claimed. 



A culture of Cladosporiuni cuvumerimim on carrot was taken and 

 a small portion of the substratum heavily covered Avith mycelium 

 and spores were immersed in a '2^/c Bordeaux mixture for two hours, 

 taking care to agitate the spore bearing material in the spray and 

 bring it actually in contact with the solution. 



After two hours the fungus w'as removed, washed thoroughly in 

 distilled water after a preliminary washing in a Gooch crucible 

 submerged partially in a gently flowing current of water for some 

 time, and then spores from the material were placed in hanging 

 drops in Van Tieghem cells. 



On examination of the spores after 26 hours it was found that 

 90% of them had germinated, indicating that Frank's work Avas 

 correct. ' Immersion in a spray is not to be compared with condi- 

 tions in the field, however, since in that case the fungicide has dried 

 on the host in the pres-ence of the various chemical agents in the 

 atmosphere, and many chemical changes have occurred Avhich alter 

 the value of the spray to quite an extent. This has been pointed 

 out by Wallace in his work on lime sulphur. He points to the fact 

 that the only method Avhich ajyproximates natural conditions is 

 where the fungicide is alloAved to dry before it is brought in con- 

 tact with the spores. 



The method developed by Wallace and Reddick' is the best means 

 of making tests of fungicides in the laboratory and comes very 

 close to conditions in nature. This was the method on which the 

 following tests were based with slight alterations in the methods. 



Wallace's method consists of spraying one-half of a glass slide 

 with the spray to be tested, leaving the other half blank to serve as 

 a check. The slides are allowed to dry under atmospheric con- 

 ditions for some time and are then ready for the tests. In making 

 these a suspension of the spores is made and a drop placed on each 

 end of the slide. These are kept moist and when sufficient time 

 has elapsed the drops are examined and the percentage of germina- 

 tion on each and determined by count under the microscope. The 

 comparsion of germination on the check and on the sprayed end 

 will give a fair idea of the value of the fungicide. 



7. Wallace, E. and Blodgott, F. M. Cornell Diillotin 290, pp. 167-179, 1911. 



