1902] TOXIC PROPERTIES OF COPPER COMPOUNDS 47 
injected with food solutions. In many cases upwards of thirty 
germ tubes were counted growing into a single stoma. On 
injecting similar leaves with pure water, however, I got a similar 
result. The leaves used were chiefly from 7vadescantia discolor. 
The concentrations of copper, cobalt, etc., injected ranged from 
0.01 to 0.005 2. 
I then tried Miyoshi’s method of using perforated mica 
plates with layers of media between. Spores were sown in 
every conceivable way: in upper, middle, and lower layers; in 
nutrient and non-nutrient media; and in media containing copper. 
The uniform result of these tests was that the germ tubes near 
the perforations grew towards the opening éf it communicated with 
@ layer of media in which no spores had been placed. The presence 
or absence of copper was not found to have any influence on the 
direction of growth. The hyphae grew towards, and in cases 
where the concentration of copper was not too great, grew 
through the perforation into the copper-containing medium. 
Fig. 6 illustrates such a case. The spores of Rhizopus were 
sown in a rich nutrient agar. Upon germination they imme- 
diately turned towards a perforation in the mica plate which _ 
communicated with a non-nutrient agar impregnated with 0.005” ~ 
. Finally, I prepared a series of cultures in large Van Tieghem | oe 
cells 5°" in diameter. The nutrient agar in which the spores — 
Were placed occupied the part marked a in fig.7. The portions ; 
- agar marked 64 were prepared from nutrient or non-nutrien 
ied to which varying concentrations of copper had been added : oo 
The Portions ¢¢ are checks, being duplicates of 64 without the 
copper. The inoculation was made by placing a few spores of = 
eee. on at the center of a. The cultures were then placed in : o 
- Incubator at 28° C. until the fungus had made consider- 
; le gr owth. The cells were then opened and 66 and cowere 
5 towards @ until in slight contact and occupying the posi- — — 
Beze ep : ce Ree a ee 
6 id and c’c’. More or less of the Cu in solution in 6’ and 
ild then pass into @, and if the fungus was either attracted — 
