Studies on Fungicides — III 59 



of water plus the hypothetical dissolving agent secreted by the spores. 

 They report (page 187 of reference cited) : 



Some drops of the filtrate were placed on slides sprayed with lime-sulfux 1-25 and some 

 on clean slides. Germination tests in water in which no spores had previously germinated 

 were carried through the entire experiment as a check. All slides were kept in moist chambers 

 for two days, then the water from each slide was removed to clean ones, and spores added. 



The germination results were as follows: control, 40 per cent; water from 

 sprayed slide, 8 per cent; water plus spore filtrate from clean slide, 25 

 per cent; and water plus spore filtrate from sprayed slide, per cent. 

 A near duplicate of this experiment gave somewhat similar results. 



Experiments. The method employed by the author was in principle 

 similar to that of Wallace, Blodgett, and Hesler. In some preliminary 

 experiments the results were not satisfactory, largely because of an apparent 

 staling effect of the water in which the spores had germinated. The 

 spores employed here were those of Botrytis allii. In all later tests, 

 conidia of Sclerotinia americana were used and excellent results were 

 obtained. This modification, together with a greater familiarity with 

 the method, resulted in the elimination of the staling-effect factor. 



The fungicides used were colloidal bordeaux membranes from 4-4 DO 

 bordeaux mixture, and copper-lime dust. The colloidal membranes were 

 separated from the mixture by centrifuging. The clear limewater and 

 lime particles were thus eliminated. Neither the original bordeaux 

 mixture nor the bordeaux membranes showed any free copper by the 

 potassium-ferrocyanide test. The bordeaux membranes were sprayed 

 into petri dishes and allowed to dry for 12 hours. With the copper-lime 

 dust, the petri dishes were first sprayed with distilled water, and then 

 the dust was applied and allowed to dry likewise. 



Spores of Sclerotinia americana were placed in distilled water in open 

 petri dishes and allowed to germinate for 12 hours. The germination 

 period was thus reduced because in nature spores would not normally 

 germinate for as long periods as two and three days before fungicidal 

 action would become operative. In all cases the germination was uni- 

 formly about 97 per cent. These suspensions were then filtered, and 

 the resulting solution constituted the " old spore filtrate." Ten cubic 

 centimeters of this was added to each of a number of petri dishes, in 

 which the bordeaux membranes or copper-lime dust had been placed 

 previously. At the same time, ten cubic centimeters of distilled water 

 was placed in an equal number of petri dishes, likewise coated with 

 bordeaux membranes or copper-lime dust. The remainder of the old 

 spore filtrate was stored in a Pyrex beaker. All preparations were 

 allowed to stand exposed to the air for 36 hours, and then filtered. 



Twelve hours previous to this filtering, a fresh spore suspension had 

 been prepared and allowed to germinate for 12 hours. This suspension 



