FROMME: THE CULTURE OF CEREAL RUSTS 519 
with transfer of infection once a week. During this period the 
rust went through 37 generations of the uredo stage. No decrease 
in the degree of infection secured resulted from such continuous 
culture. 
2. The average degree of infection maintained in mass cultures 
was approximately 200 pustules per, plant. The largest number 
of pustules counted on an individual plant was 996. 
3. P. coronifera does not self-propagate to any extent even when 
abundant host material is supplied and a constant humidity of 
93 per cent is maintained. 
4. High humidity is the essential factor in securing successful 
inoculation with uredospores of P. coronifera. No infections 
resulted when cultures were exposed in an atmosphere of 75 to 80 
per cent of humidity, and at 93 per cent only 6 per cent of the 
normal degree of infection was obtained. Normal infections were 
secured only when cultures were covered with a bell jar for twenty- 
four hours subsequent to the application of spores. 
5. The rate of development of P. coronifera increased with tem- 
perature increase. A decrease in the normal incubation period of 
five days, or 41 per cent, was produced in the ‘‘stove” where the 
temperature ranged from 20° to 30° while the range at which the 
normal cultures were grown was 14.5° to 21°. 
6. Total light exclusion either early or late in the incubation 
period checks the development of P. coronifera and results in an 
almost complete cessation of growth. 
7. Uredospores of P. coronifera when stored at room tempera~ 
ture gradually lose their capacity for germination. A 0.2 per cent 
germination was obtained after storage of eighty-four days. 
COLUMBIA UNIVERSITY, NEW YORK. 
LITERATURE 
1. Balls, W. L. Infection of plants by rust fungi. New Phytol. 4 
18, 19. 1905. 
2. Barclay, A. On the life-history of Puccinia coronata, var. hima- 
lensis. Trans. Linn. Soc. II. 3: 227-242. pl. 56. 1891. 
3- Bary, A. de. Untersuchungen iiber Uredineen. Monats. Akad. 
Berlin 15-50. pl. 1. 1866. 
4. Bary, A. de Neue Uiterescueees iiber Uredineen. Monats. 
Akad. Berlin 205-216. pl. 1. 1867. 
