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SOME FUNGOUS DISEASES OF THE GREENHOUSE. 



By W. Lochhead, Macdonald College. 



1. Carnation Eust (Uromyces caryophyllinus (Schrank) Wint.) 

 Florists find much trouble in controlling the disease commonly known 

 as Carnation Rust, although it has been known in Europe for over a cen- 

 tury. Few records of its occurrence in Canada are to be found before 

 1890, and on its first appearance carnation growing was seriously threat- 

 ened. It was soon found, however, that certain varieties were more re- 

 sistant to the rust fungus than others; accordingly, rust-resisting varie- 

 ties have largely supplanted the susceptible varieties. Moreover, the 

 growers have discovered that the spread of the rust depends to a consid- 

 erable extent on the conditions under which the plants are grown, hence 

 greater attention than formerly hds been given to matters of sanitation 

 and cultivation. 



Carnation Rust, as the name implies, is a fungus belonging to the 

 family of Rusts, the most familiar example being wheat rust. Two kinds 

 of spores are formed, — uredospores or summer spores and teleutospores 

 or winter spores, both often growing together in small pustules on both 

 sides of the leaf and on the stem. The pustules from under the epidermis 

 finally ruptures, exposing the dark brown spores in elongated patches. 

 The uredospores when observed under the microscope are nearly spher- 

 ical and have thick walls which are sparsely covered with small spines. 

 They germinate immediately in water. The teleutospores are about the 

 same size but more elliptical and possess minute v»^art-like markings. 

 They do not germinate until spring. The vegetative portion of the 

 fungus, composed of threads, termed the mycelium, lives within the tis- 

 sues of the plant, and continues to produce successive crops of pustules 

 of spores during the remainder of the life of the plant. This habit of the 

 mycelium makes it imperative that cuttings should not be taken from 

 diseased plants. It is probable, moreover, that mature plants may be 

 inoculated by spores of the fungus under suitable conditions and that the 

 disease may rapidly spread through the beds. 



Treatment. — ^While it is very difficult to prevent the development of 

 carnation rust, experience proves that it can be controlled to such an extent 

 that carnation culture may be carried on successfully. The means adopted 

 are: (1) the growing of rust-resistant varieties of carnations, such as the 

 Enchantress and Lawson; (2) attention to the watering and ventilation of 

 the plants by placing supports of wire-mesh between the rows to prevent 



