206 THE PRINCIPLES OF FLORICULTURE 



194. Ecology of the carnation rust disease. Faulty venti- 

 lation which produces close, humid conditions, and any cultural 

 treatment which induces a soft, succulent growth, favor the 

 development of the parasite. 



195. Preventives. Propagate only firm, strong, disease- 

 resistant stock, such as present-day breeders are now producing. 

 Give careful attention to all cultural details, especially ventila- 

 tion. Syringe the plants only on bright, sunny days. Fungi- 

 cides are sometimes used as preventives. They assist in keeping 

 the plants healthy, but these should be of such a character that 



ythey do not make the foliage unsightly. Bordeaux mixture will 



*** do this. Before the cuttings are potted, they may be sprayed 



with a solution of copper sulfate, using a fine spray to cover 



both sides of the leaf. After the plants are established in thumb 



pots, it is well to spray a second time. 



196. Remedies. There are no remedies, so far as known, for 

 carnation rust. If plants are infected, they should be removed 

 and burned. The benches should be thoroughly white-washed 

 and fresh soil used. 



197. The rose rust. Classification: Uredineae, Phragmidium 

 subcorticium Schrank ; and speciosum Fr. Of the two species of 

 rose rust, Phragmidium subcorticium is the most common. It is 

 rarely found on roses under glass, but confines its attacks princi- 

 pally to the leaves of hybrid perpetuals and other outdoor species. 

 Phragmidium speciosum usually attacks the stems. 



198. Microscopical nature of rose rust. Its microscopical 

 nature is not unlike that of the carnation rust. All forms of 

 spores, however, are produced by these species. 



199. Ecology of disease. The vigor of rose plants weakened 

 by imperfect drainage, or other soil conditions, may be respon- 

 sible for this disease. 



200. Preventives. Occasional sprayings with Bordeaux mix- 

 ture or ammoniacal carbonate of copper assist in preventing 

 rose rust. It is well to spray early in the season before the 

 disease becomes established. Phragmidium speciosum rarely ap- 

 pears until late in the season. If the disease is present, all 

 tissue should be removed and burned. Leaves from the rose 

 bed should be gathered in the fall and burned, to destroy the 

 teleutospores. 



There are no known remedies for the rose rust. 



201. Basidiomycetes. In Basidiomycetes, the spore-bearing 

 cells are called basidia. These are of definite shape and have 

 lateral branches, called the sterigmata. From these, a definite 

 number of basidiospores are abjointed, the basidia then becom- 



