ON SO Sith es Re eae ve Zod alte Fa ie alae se i ed re 
eat ee fe PEP ENE. Choe ere iE, Lg 
oa iP aS ead os EA BR hs ake di ake ee ee oo i area tea keel ee 5 oo iit 
1902] TOXIC PROPERTIES OF COPPER COMPOUNDS 45 
contents of pollen grains and the cells of the stigma have an 
unusually solvent action on the copper hydroxid. 
Swingle’s proposition that the copper might be effective in 
preventing the attack of parasites through negative chemotactic 
action induced me to make a number of experiments on this 
point. A number of fungi were used to a greater or less extent, 
Fic. 5. 
but Rhizopus proved the most satisfactory, inasmuch as it 
usually germinates with a single germ tube and grows rapidly 
with a minimum of branching. 
The well-known method of Pfeffer was first employed. 
Capillary tubes closed at one end were filled with solutions of 
Copper of varying strengths. Hanging drop cultures of the 
fungi were prepared in weak agars of varying consistence. Into 
these hanging drop cultures were introduced the open ends of 
the copper-containing capillary tubes. These tubes were intro- 
duced at different stages of germination. The uniform result of 
