New York Agricultural Experiment Station. 57 



membrane short branches have been produced at the ends of 

 which spores are formed. When ripe the spores drop from their 

 stalks, and others are formed in their places.^ 



THE RUST. 



Carnation rust is distinguished from other rust-colored 

 traubles of the leaves by the presence of brown spores, which are 

 liberated by the bursting of the " blister " in which they are 

 formed. Each spore is normally capable of germinating and 

 developing into a fresh spot of rust. Moisture and warmth are 

 necessary to the best development of this fungus, hence warm, 

 moist houses are more seriously infested than cool, dry ones 

 growing the same varieties. Different varieties of carnations are 

 subject to the rust in degrees varying with the variety. There 

 seems to be some relation between the presence of " bloom " upon 

 the leaves and immunity to the rust, as those varieties which 

 have the most bloom are among those which rust but little. The 

 rust usually does little real injury to the plant but in severe 

 cases it may seriously check the natural growth of the host. 



Once infested the plant continues to be rusted until destroyed. 

 The hyphie of the fungus penetrate the leaf and stem-tissue and 

 produce here and there the pustules of spores, which are the visi- 

 ble evidence of the rust plant. Cuttings taken from a rusted 

 parent produce rusted plants^, indicating the presence of the fun- 

 gus hyphte in the actively growing portions of the plant. When 

 the rust spores germinate they gain access to the interior of the 

 leaf either through a stomate or some weak or broken spot in 

 the leaf. From such a point as center the disease spreads 

 through the cells of the host, securing the needed nourishment 

 from these cells. It is now safe from any external treatment; any 

 checks to its further development must be able to reach it within 

 the tissues of the host and yet do no material injury to that host. 

 Such a check is the fungus Darluca filum. 



"Sapin^Trouffy in Le Botaniste, 5: 51. 



'Statement made by carnation growers of experience. 



