62 S. E. A. McCallan 



However, regardless of these; possibilities, these experiments seem to 

 demonstrate definitely, at least on the part of germinating spores, an 

 excreted solvent capable of dissolving copper from "insoluble" copper 

 protectants. 



The action of spore excretion* on bordeaux mixture in dialyzing sacs 



Hypothesis. If bordeaux mixture containing' no free copper is placed 

 in a suitable dialyzing membrane immersed in water, it may be assumed 

 that the colloidal bordeaux membranes will not be able to diffuse out- 

 ward. The dialyzing membrane, however, should allow the outward 

 and inward diffusions of materials in solution. A solvent action on the 

 part of the spore excretions being assumed, then, if the fungus spores 

 are placed in water on the outside of the dialyzing membrane, the excre- 

 tions will pass through the dialyzing membrane. Here reaction will take 

 place with the bordeaux membranes, and by reason of the solvent powers 

 of the spore excretions some copper will be brought into solution. This 

 soluble copper will diffuse outward and react with the fungus spores, 

 inhibiting their germination and ultimately killing them. 



Experiments. Collodion dialyzing sacs were prepared according to 

 the method of Eggerth (1921), d'Herelle (1926), and Mulvania (1926). 

 The porosity of these sacs varies according to the ratio of alcohol and 

 ether; a greater degree of porosity is obtained by increasing the percent- 

 age of alcohol. The first collodion sacs prepared were of the formula 

 23-77-1.5; that is, 23 cubic centimeters of absolute ethyl alcohol, 77 cubic 

 centimeters of ethyl ether, and 1.5 grams of soluble nitrated cotton. 

 The sacs were molded on the inside of 1.5x1 1-centimeter test tubes. 



Bordeaux mixture (4-4-50) was prepared and tested for free copper. 

 None was found. The bordeaux was then placed inside the collodion 

 dialyzing sacs. The mouths of the sacs were tied with string and sealed 

 with collodion. After this the sacs were thoroughly rinsed in distilled 

 water and then placed in open petri dishes. Fresh distilled water was 

 added to the dishes so that the sacs were just submerged. Two sacs 

 were placed in each dish. The dishes were then divided into two lots. 

 To one there was added a concentrated suspension of conidia of Sclerotinia 

 americana. The other remained standing without spores. After two 

 to three days the spores of the first lot were examined for germination. 

 At this time the bordeaux-containing sacs were removed from the second 

 lot of dishes and a suspension of spores was added to the remaining liquid. 

 After standing thus for another two days, these spores were in turn 

 examined for germination. This was to test for any possible outward 

 diffusion of copper. Controls were carried throughout, in which a sus- 

 pension of the spores had been placed in dishes containing dialyzing sacs 



