Antirrhinum Diseases 201 



add to the soil a liberal application of rock phosphate 

 and finely ground limestone. Antirrhinums thrive 

 very poorly in wet soils. The plants should not be 

 syringed in winter and especial care should be taken 

 in watering on cloudy days. The plants are not in- 

 jured by a night temperature of 45 degrees F., al- 

 though 48 to ^s degrees suits them' best. The day 

 temperature should never run above 70 degrees F. 



Diseases of the Antirrhinum 



The antirrhinum, although considered a hardy 

 plant, is subject to several diseases, most of which 

 are of economic importance. 



Rust 



Caused by Puccinia antirrhini Diet, and Halw. 



Symptoms. The Uredo stage is the one most 

 commonly found. It is manifested as small round- 

 ish, reddish brown pustules, usually grouped circu- 

 larly on the under side of the leaf or on the stem 

 (fig. 40, a and b). The affected tissue becomes yel- 

 low. The fungus was first described by Dietel* who 

 foimd the Teleuto and the Uredo stage on specimens 

 collected in California. The fungus is very com- 

 monly foimd to attack snapdragons out of doors. 

 It is also a serious trouble to growers of greenhouse 

 plants. However, the Teleuto stage is not fre- 



•Hedwigia, 36:298, 1897. 



