RUST OF ANTIRRHINUM. 65 



10. If rust appears the temperature should be run up to 60° F. at night 

 for a few nights, till the rust has been placed under control by sulfuring 

 or hand picking. ' It should be borne in mind that 50° F. is the tempera- 

 ture most favorable to the fungus. 



SUMMABY. 



Puccmia Antirrhini Diet, and Holw. is known to occur only on An- 

 tirrhinum majus. 



This rust is the most serious disease of snapdragons under glass, and 

 is second in importance to anthracnose on snapdragons out of doors. 



The urediniospores germinate moderately well with an optimum tem- 

 perature of 10° C; the teliospores have not been germinated. 



Dry in-ediniospores do not retain the power of germination more than 

 six weeks. 



No varieties of snapdragon are absolutely resistant to the parasite, 

 but some are relatively resistant. The varietal resistance is dependent 

 on the relative number of stomata per unit area of leaf surface. 



The urediniospores are disseminated by cuttings, insects, w^ater and 

 wind. 



A 0.25 per cent solution of copper sulfate is toxic to the urediniospores 

 of P. Antirrhini. 



A 0.25 per cent solution of cuprammonium sulfate is toxic to the ure- 

 diniospores of P. Antirrhini. 



Bordeaux mixture is not toxic to the urediniospores of P. Antirrhini. 



The SOo generated by dry sulfur at a temperature of 21° C. is toxic 

 to the urediniospores of P. Antirrhini. 



The method of control recommended consists in growing resistant 

 varieties, controlling cultural conditions carefully, dusting with powdered 

 sulfur at a temperature of 70° F., and keeping the night temperature 

 of the snapdragon house above 52° F. or below 48° F. 



Literature Cited, 



Atkinson, G. F., 1890. Chrysanthemum Rust. Botanical Gazette, 15: 166. 

 Howell, J. K., 1890. The Clover Rust. Bull. 92, N. Y. (Cornell) Agr. Expt. 



Sta., pp. 127-139. 8 figs. 

 Cobb, N. A., 1892. Contributions to the Economic Knowledge of the Australian 



Uredinese. Agr. Gaz., New South Wales, 3 (3): 181, 182. 

 Maynard, S. T., 1893. Carnation Rust. Hatch Expt. Sta., Mass. Agr. College 



Rept. for 1892, pp. 157, 158. 

 Hitchcock, A. S., and Carleton, M. A., 1893. Preliminary Report on Rusts of 



Grain. Bull. 38, Kans. Agr. Expt. Sta., pp. 1-14. Pis. 1-3. 

 Pammel, L. H., 1893. Experiments with Fungicides. Bull. 24, Iowa Agr. Expt. 



Sta., pp. 985-990. 

 Stuart, W., 1894. Carnation Rust. American Florist, 9: 1231, 1232. 

 Bailey, L. H., and Lodoman, E. G., 1895. Forcing House Miscellanies. Bull. 



96, N. Y. (Cornell) Agr. Expt. Sta., pp. 294-.335. 

 Erikson, J., 1895. Ueber die Forderung der Pilze poren Kcimung durch Kalte. 



Cntr. F. Bact., 2: 557-565. 



