BULLETi:^ ^o. 202. 



DEPARTMENT OF BOTANY. 



RUST OF ANTIRRHINUM. 



BY WILLIAM. L. DORAN. 



Introduction. 



The cultivated snapdragon {Antirrhinuvi majus L.) is a biennial or 

 perennial under culture. It is a member of the family Scrophulariacese. 

 The plant was introduced here from Europe. As an escape from gardens 

 it is rare in New England. The snapdragon has been a popular garden 

 flower for two hundred years, but only within the last ten years has it been 

 grown to any extent as a greenhouse crop. There has been an increasing 

 demand for it as a cut flower, and consequently an increasing amount of 

 glass has been devoted to its culture. As a florist's crop, the snapdragon 

 may be classed as about equal in importance to mignonette, schizanthus, 

 stocks, pansies and primulas (Nehrling, 1914), varying, of course, in 

 different localities. 



Growers have propagated principally for the best colored blossoms and 

 the best formed spikes, and relatively slight attention has been paid to the 

 susceptibility of the plants to disease. Increased and intensive cultivation 

 seem to have weakened this once hardy plant, for it is now affected severely 

 by at least four fungous diseases. The diseases of snapdragon, other than 

 rust, are: anthracnose or leaf-spot, caused by Colletotrichum Antirrhini, 

 Stew. (Stewart, 1900), and stem-rot and leaf-spot, caused hy Phyllosticta 

 AntirrJmii, Syd. (Guba and Anderson, 1919). 



Rust is the most serious of the diseases of snapdragon under glass ; but 

 according to the observation of the writer, anthracnose is in most years a 

 more serious disease than rust on plants grown outdoors. The investiga- 

 tion of snapdragon rust was undertaken by the writer because of the 

 economic importance of the disease, and because so little information 



1 Presented to the faculty of the Graduate School of the Massachusetts Agricultural College 

 (May, 1917) in partial fulfillment of the requirements for the degree of master of science. Litera- 

 ture citations are brought up to the date of presentation for publication (January, 1921). The 

 writer wishes to express his indebtedness to Prof. A. V. Osmun of the Massachusetts Agricul- 

 tural College and to Dr. O. R. Butler of the New Hampshire Agricultural Experiment Station, 

 under whose direction the work here described was carried on. 



