562 FETCH : 



minutes, though tlie spores alone germinated after 

 an immersion of ten minutes. In the other, transfers 

 of mycelium and spores failed to grow after four and 

 half minutes' immersion, while the sj)ores alone did 

 not survive four minutes. Experiments witli other 

 fungicides usually show that the spores in the myce- 

 hum, as would be expected, survived a longer 

 immersion than the spores alone ; but even that does 

 not hold good in the present case. 



It has been shown previously by Brooks (19) that the 

 concentration of the toxic agent required to produce injury in 

 flasks is greater than that required in hanging drops. Ap- 

 parently a similar rule is true in the present case, viz., that 

 spores subjected to immersion in a toxic solution will grow 

 in flasks when they will not grow in hanging drops. To 

 whatever cause this may be due, it is evident that in order to 

 determine whether spores are dead they should be tested in 

 flask cultures, not in hanging drops. 



The impossibihty of obtaining a sample of spores, all of the 

 same power of resistance, introduces a large element of chance 

 into such experiments as those described above. For example , 

 we may imagine that a given sample consists chiefly of spores 

 which would be killed by an immersion of two minutes, in a 

 certain fungicide, but contains a few Avhich would survive ten 

 minutes but be killed by eleven minutes. If the latter spores 

 happened to be all taken in the first minute, the death point 

 of the whole sample would be two minutes. Similarly, if none 

 of them were taken in the first eleven minutes, the death point 

 of the whole would again be two minutes. And, of course, 

 all other numbers from two to ten would be possible. The 

 heterogeneity of the material renders any uniform result 

 impossible. 



Forinaldehyde, 1 -0 per Cent. 



(1) As a preliminary experiment, spores from a six days 

 old culture were immersed in 1 -0 per cent, formaldehyde, and 

 transferred at intervals to flasks of pure cane extract by 

 means of a platinum loop. Transfers 1-20 were made at 

 intervals of one minute, 21-28 at intervals of five minutes, 

 and 29-37 at intervals of fifteen minutes. Further transfers 



