Chapter XXL 



Diseases of Greenhouse and Ornamental Plants. 



Jff 



Carnation smut [Ustilago violacea (P.) Fckl.]. This smut at- 

 tacks a large number of species of the plants belonging to the 

 pink family, such as common garden-pinks and carnations, and 

 such wild flowers as catch-flies, star-worts, soap-worts and corn 

 cockles. This is a very different disease from the rust of carna- 

 tions and cannot easily be confused with it. The carnation smut 

 attacks the stamens of the flower and converts the anthers into 

 smut-spore sacs. The smut spores form a violet-colored powder 

 and one can easily mistake this for abnormally colored pollen. 

 When the smut spores escape, many fall upon the petals and 

 sepals discoloring them and rendering them unfit for decorative 

 use. This fungus often exerts a remarkable influence upon those 

 members of the pink family which have pistillate and staminate 

 flowers, e. g., the corn cockles. The pistillate flowers, when at- 

 tacked, develop stamens which, in an unaffected flower, remain 

 undeveloped. These stamens, as well as those o<f the staminate 

 flo\vers, become a prey to the smut fungus. As a general rule no 

 other parts of the flower or plant are enlarged, or in any way dis- 

 torted. There is no indication o>f the presence of the fungus, and 

 the latter can only be detected at the ripening of the spores, or by 

 a previous examination of the anthers. 



The diseased plants should be promptly destroyed to prevent 

 a spread of the disease. 



The violet smut [Urocystis violae (Sozv.) Fisch.]. Occasion- 

 ally on pansies and violets. (See Diseases of Wild Plants.) 



The chrysanthemum rust (Puccinia chrysanthemi Rose.). 

 This disease has appeared in recent years as an abundant parasite 

 on greenhouse chrysanthemums. It is not, as was formerly sup- 

 posed, identical with the common wild rust of sunflowers and 

 their allies but it is a distinct importation, probably, from Japan. 

 The summer spores are found in the fall and are produced in 



