174 BOTANICAL GAZETTE [SEPTEM BER 
UREDINIOSPORE GERMINATION.—Rusted specimens of either 
Avena fatua, A. sativa, or A. sterilis were collected from May 7 to 
December 15 inclusive at San Diego and Santa Barbara, California; 
Carrol, Missouri Valley, Onawa, and Sioux City, Iowa; Lexington, 
Kentucky; Gilliam and Shreveport, Louisiana; Albert Lea, Belle 
Plaine, Caledonia, Granite Falls, Hinckley, Pipestone, Preston, 
Saint Paul, Sauk Center, Spring Valley, Two Harbors, Virginia, 
Wabasha, and Zumbrota, Minnesota; Sedalia and Springfield, 
Missouri; Pembina, North Dakota; Brookings, Bushnell, and 
Newell, South Dakota; Jackson, Knoxville, and Nashville, Ten- 
nessee; Beaumont and San Antonio, Texas; Lynchburg, Virginia, 
and Madison, Wisconsin. The freshly acquired material was 
treated in the same manner as were the specimens of the aecio- 
sporic stage. After a maximum period of 87 days from date of 
collection, the urediniospores collected on A. sativa were still viable. 
To determine the possibility of differences in the germinating 
capacity of urediniospores secured on various hosts in different 
localities, when subjected to similar environmental conditions, the 
following series of greenhouse inoculations was devised: 
a) Rusted specimens of A. sativa were collected at Saint Paul, 
Minnesota. The spores were used as the original inoculum for 
infecting Improved Ligowa Oats (Minn. 281). Spores obtained as 
a result of this infection were again used as a source of inoculum 
for another set of the same host. This procedure was continued 
for five successive spore generations. 
b) Rust collected on A. sterilis at Saint Paul, Minnesota, was 
used as the original inoculum for infecting the same host as that 
mentioned in the preceding case. The subsequent procedure was 
the same. : 
c) The original inoculum for the third series was identical with 
that described in the second series. The successive inoculations 
resulted in two spore generations being developed on Improved 
Ligowa Oats (Minn, 281), one generation on A. sterilis, followed by 
two generations on Improved Ligowa Oats (Minn. 281). 
d) Rusted specimens of A. sterilis were collected at Lynchburg, 
Virginia. The spores were used as the original inoculum. Sub- 
sequent inoculations resulted in five spore generations being devel- 
