242 PLANT DISEASES 



extends itself throughout the summer months. When the 

 leaves are fading, the teleutospore form of fruit is produced, 

 which differs from the uredo form in the pustules being 

 darker in colour, and not powdery. The aecidium stage 

 is absent. 



The teleutospore stage has not up to the present been 

 observed on the chrysanthemum, and some observers 

 consider the uredo as belonging to Pucdnia tanaceti. 



Preventive Means. — Spray at intervals, dating from 

 the growth of new leaves, with potassium sulphide solution, 

 which not only destroys the rust-spores, but also those of 

 various other fungous pests that attack chrysanthemums. 

 Remove plants showing the slightest trace of disease. 



If the disease has existed, be careful to destroy all leaves 

 that may be likely to produce teleutospores, otherwise a 

 recurrence of the disease is practically certain. In the 

 case of plants grown in houses, the uredo form will continue 

 throughout the winter on the living leaves, therefore a 

 constant watch for the fungus is necessary. 



Finally, this fungus is by no means uncommon on a 

 score or more wild species of plants belonging to the 

 Compositae, and care should be taken not to allow the 

 disease to be introduced by such outside sources ; the 

 fungus is especially common on wild species of hawkweed 

 {Hieracium), hence its specific name. 



There is no reason why this fungus should not, in 

 course of time, attack other cultivated composite plants, 

 as cinerarias, dahlias, etc. 



Massee, in Gardeners' Chronicle, and Gardeners' Maga- 

 zine, with figs., Oct. 8th, 1898. 



