232 Forestry Quarterly. 



taken and the entire currant plantation of the station was de- 

 stroyed. Since that time no signs of the disease have been found 

 at Geneva. This outbreak of the currant rust has been fully re- 

 ported in Technical Bulletin, No. 2 of that Station. 



As already stated, the disease has two forms of spores which are 

 produced on the two different plants. The spores which are pro- 

 duced on the underside of the Ribes leaves appear during the sum- 

 mer and autumn (probably in August and early September) as 

 orange-colored powder having somewhat the appearance of coarse 

 yellow plant hairs. These spores (uredo-spores) when mature 

 may be carried by the wind to adjacent White Pine trees. There 

 they germinate, and the mycelium grows in the soft inner bark of 

 the pine. The period of incubation in the White Pine is not com- 

 plete the first spring after infection, but often during the 

 coming summer infected stems or branches show a thickening 

 and apparent swelling. The following spring (probably 

 middle of April, or May and early June) the disease breaks 

 through the bark and the light orange-colored fruiting bodies, 

 which are about one-eighth inch thick, project from the diseased 

 pine branch or stem. These spore cases soon rupture and the 

 spores are desseminated. The spores from the pine (aecidio- 

 spores) may infect any Ribes leaves with which they come in con- 

 tact. The period of incubation on the Ribes is much shorter 

 (varying from fifteen to forty days) resulting in the breaking 

 out of minute, yellow pustules, the uredo-spores, which on opening 

 emit a yellow dust, which may again infect either other Ribes or 

 White Pine, while the aecidio-spores which are produced on the 

 pine can infect only Ribes, i. e. the disease can not be transmitted 

 direct from pine to pine. Toward the end of the summer the yel- 

 low spots on the currant leaves become darker, and hornlike out- 

 growths are found on them. On these horns new spores are 

 formed. These "teleuto-spores" germinate and produce small 

 bodies called sporidia, and it is only these sporidia which are again 

 capable of germinating on White Pine and producing the blister 

 rust. 



Some facts in regard to the discovery of the disease may be 

 of interest. Last spring the Forest, Fish and Game Commission 

 of New York received a large consignment of trees from J. Heins' 

 Sonne, Halstenbeck, Germany, in order to satisfy the demand for 

 reforesting stock. When these trees were being unpacked one of 



