66 S. E. A. McCallan 



The water standing in the watch glasses sprayed with bordeaux was 

 filtered, and the filtrate was added to the clean slides holding the spore- 

 suspension drops, so that it formed a covering film. This film resembled 

 that of the distilled water on the other set of slides. This set constituted 

 a check on the copper that, might come into solution from the bordeaux 

 through atmospheric agencies or other means. 



A control was maintained, in which films of distilled water were placed 

 over drops of spore suspension. All slides were placed in moist chambers 

 and the usual germination tests were made. The usual type of control 

 also was carried. 



The germination results after 24 hours are recorded in table 15. 



TABLE 15. Sphere of Influence of Spore Excretions: Percentage Germination 



OF SCLEROTINIA AMERICANA CONIDIA 



Treatment 



Per cent and 



type of 

 germination 



Bordeaux filtrate on spores 



Bordeaux areas near spore areas, distilled water over all. 



Water-film control 



Control, usual (spores 6 days old) 



58.2 B 





 96 5 \ 

 97.8 A 



The reduced germination in the case of the filtrate is doubtless due in 

 large part to soluble calcium compounds. The ungcrminated spores here 

 appeared normal, which is characteristic of spores killed by Ca(OH) 2 

 and CaS0 4 . However, the spores that were placed near the areas of 

 bordeaux mixture showed a very evident precipitation of their contents, 

 a condition characteristic of. copper poisoning. 



This experiment was elaborated in some detail. Drops of bordeaux 

 mixture (no free copper) were placed, one each, on a number of slides and 

 allowed to dry down. Then to one slide was added a drop of Sclerotinia 

 americana spore suspension, and an additional second drop twice as far 

 from the edge of the bordeaux as the first drop. On a second slide there 

 were placed three drops of the spore suspension, on a third slide four 

 drops, and on a fourth slide five drops. A slide with five drops is dia- 

 grammatically illustrated in figure 4. This series was made up in quad- 

 ruplicate. The spores were allowed time in which to settle and adhere 

 to the glass. The average distance between the edge of the bordeaux 

 area and the edge of the nearest spore-suspension drop was 7.5 millimeters. 

 Drop no. 2 was 15 millimeters distant, no. 3 was 30 millimeters, no. 4 was 

 40 millimeters, and no. 5 was 50 millimeters, Regardless of the number 

 of spore-suspension drops on each slide, these distances were maintained. 

 The number of spore-suspension drops was varied in order to further 

 study the correlation between total toxic substance and number of spores, 

 which has already been discussed in the copper-toxicity studies. 



