May 19,1923 
Life History of Stripe Rust 
609 
tion stations were established near Corvallis, Oreg., with a number of 
wild grasses which were naturally infected with stripe rust. Plants of 
Hordeum nodosum L., Bromus marginatus Nees, and Elymus glaucus 
Buckl. were chosen for these observations. At no time during either 
winter was it impossible to collect viable urediniospores at any of these 
observation points. Viable urediniospores were collected upon Elymus 
glaucus in 1917--18 in every month from September, 1917, to July, 1918, 
inclusive. 
There is some evidence also which indicates that the fungus may 
overwinter in the uredinial stage in the intermountain regions, between 
the Cascade and Rocky Mountain Ranges. Willis (jj) reports that the 
rust may overwinter at Moscow, Idaho, on Hordeum jubatum. The 
author also obtained evidence from observations made in the spring of 
1920, and again in 1921, that the uredinial stage of the fungus may sur¬ 
vive the winter in northern Idaho. Plants of Hordeum jubatum and 
Bromus marginatus^ which were heavily infected in the fall, developed 
fresh uredinia in both 1920 and 1921, soon after the snow melted in the 
spring. In the fall of 1921, various infected hosts in the grass nursery 
at Moscow, Idaho, and also other hosts located at various places near 
Moscow, were marked and were examined as soon as the snow melted 
in the spring. Snow covered these plants continuously from the last 
week in December until the middle of March. Oh April 3, 1922, several 
uredinial sori were found on an old leaf of a seedling of Hordeum nodosum 
growing beside a mature plant of the same species which was heavily 
infected in the fall. None of these sori had broken through the epidermis 
of the leaf. The spores were perfectly normal although immature. . The 
appearance of the leaf seemed to indicate that infection had taken place 
in the fall and after remaining dormant through the winter had started 
to develop thus early in the spring. By April 15 a number of seedlings 
of this grass were found infected and producing urediniospores in abund«- 
ance. 
OVERSUMMERING UREDINIA 
Observations made during the last five years indicate that along the 
Pacific coast of Washington and Oregon it is much more difiicult for the 
rust to survive the dry summer monfiis of July and August than to pass 
through the winter. The summers of 1917 and 1918 were exceedingly 
dry in the Willamette Valley of Oregon where observations were made 
during those two years. In 1917 there was no rainfall from June 8 until 
September 10, and in 1918 from June 5 until September 12. Needless 
to say, practically all of the wild grasses were completely dried up and 
very little rust infection of any kind was to be found by September. 
Observations were made at Corvallis, Oreg., throughout the summer of 
1917 upon Elymus glaucus^ Bromus marginatus y and Hordeum nodosum, 
all of which hosts were heavily infected with stripe rust during the month 
of May. The Elymus glaucus plants were located on the banks of a small 
creek near the college farm. Urediniospores were produced in abund¬ 
ance upon these plants during May and the first half of June. Infection 
became gradually less until about July 20, after which no new ure¬ 
diniospores were produced until after the fall rains began. During this 
period, from July 20 to September 8, the Elymus glaucus plants made 
very little new growth, but a few leaves retained their green color. The 
old lesions or stripes showed plainly upon these half-dried leaves, but 
