572 FETCH : 



Transfers of spores from copper sulpliate to hanging drops 

 of cane extract were not made. 



The lack of any uniformity in the foregoing figures is in 

 striking contrast to tlie regularity observed in tlie experiments 

 on the inhibition of germination by toxic agents, &c. In the 

 latter, it was possible to carry an experiment on up to a certain 

 percentage, and then to begin another series at that percentage 

 with a different sample of spores, with the certainty that the 

 first result would be repeated. For instance, spores sown in 

 a nutrient medium with ■ 1 carbolic acid produced submerged 

 mycelium only ; in another series, beginning witli • 1 per cent, 

 carbolic acid, the same result was obtained. Gallic acid and 

 sodium chloride provide two other examples. Moreover, in 

 the preliminary tests, it was determined whether the fungus 

 would grow in solutions which contained 0-5, 1-0, and 1 • 5 per 

 cent, of the toxic agent ; and in no case did the limit in the 

 succeeding experiment exceed that found in the preliminary 

 test, though the former was made witli another sample of 

 spores. Apparently, therefore, the percentage of a toxic 

 agent which will inhibit germination is about the same for 

 all samples of spores, but the time required to kill the spores 

 by a given percentage differs witli different samples. 



From the table on page 571 , the order of the four substances 

 arranged according to their fungicidal value is mercuric 

 cliloride, formalin, carbolic acid, copper sulphate. Arranged 

 according to their power of inhibiting germination, the order 

 is mercuric chloride, formalin, copper sulphate, carboMc acid. 

 With Thielaviopsis at least the real fungicidal value of copper 

 sulphate is remarkably low. 



Though no definite result was obtained in this second 

 series, the following conclusions appear to be warranted by the 

 foregoing experiments : — 



(1) Tests of fungicides, which determine only the percentage 

 required to prevent germination, do not give a true idea of 

 their actual or relative fungicidal value. 



(2) Spores which are subjected to the action of a fungi- 

 cide of such concentration as to inhibit germination 

 remain dormant, and may germinate when the fungicide is 

 removed. 



