206 
E. B. MAINS 
Sterile Petri dish. Evaporation from the drops was prevented by 
either having absorbent paper moistened with the nutrient solution 
used in the bottom of the dish or by having a small amount of the 
solution alone. If absorbent paper was used, a V-shaped piece was 
cut out so that the microscope could be used to observe the develop- 
ment of the rust in the hanging drops, each of which in turn could be 
brought over the V-shaped opening by turning the cover upon the 
bottom part of the dish. 
The germination could be watched under the i6 and 8 mm. objec- 
tives with clearness and the growth and condition of the germ-tubes 
could be easily followed. Each Petri dish had ten hanging drops on 
its lid and since three Petri dishes were used for each solution thirty 
hanging drops were employed for each nutrient medium. 
Some contamination resulted in these cultures, but most of the 
hanging drops showed only a slight growth of saprophytic fungi during 
the short time that cultures were run. 
Experiment 41. — The nutrient media used in this experiment were 
conductivity water, cane sugar i percent, cane sugar 5 percent, maltose 
I percent, maltose 5 percent, leucine i percent, asparagine saturated 
solution, asparagine i percent and peptone (Witte's) i percent. Be- 
sides these, a mineral solution, and carbohydrates plus the mineral 
solution were used. The mineral solution used was Duggar's standard 
nutrient solution (1909) for fungi minus the sugar. It consisted of the 
following, dissolved in 100 cc. of water: 
The cultures were kept at 17° C. during the experiment. The 
following table gives the results of the experiment. 
Since a dense mass of hyphae was produced during the germination 
of the spores, the number of germinated spores could not be accurately 
counted and the amount of germination was estimated by the appear- 
ance. In the column under remarks the germ-tube is described whether 
it produced short side branches or was unbranched. In all these 
solutions, the rust was dead in about four days. 
Experiment 42. — Since the preceding experiment indicated that 
strong concentrations were injurious to spore germination and that 
NH4NO3 
KH0PO4 
MgS04. 
FeCls. . . 
1. 00 gm. 
.5 gm. 
.25 gm. 
trace. 
