42 EXPERIMENT STATION. ' [Jan. 



The white pine (Pinus Strohus) blister rust {Peridennium 

 Strobi) has only been known in Germany for the last thirty or 

 forty years. In this country it has been discovered within the 

 last few years. In 1906 Dr. F. C. Stewart of the Geneva sta- 

 tion in New York found the disease on the grounds there, but 

 prompt and radical treatment is believed to have completely 

 eradicated it. Again, in 1909, it was found in New York State 

 on a shipment of three-year-old white pine seedlings from 

 Germany. 



This fungus has two well-known forms which have in former 

 years been described as two distinct species, — one appearing 

 on the currant and gooseberry (Ribes), and the other on the 

 white pine. The stage found on the Ribes bushes was discov- 

 ered and named about fifty years ago by Dietrich, while the 

 stage on the pine was discovered and named by Klebahn in 

 1887. Since this time, however, by careful and extensive inoc- 

 ulation experiments, it has been conclusively proved that Peri- 

 dermium Strohi on the pine, and Cronartium ribicola on Ribes 

 are not two dis-tinct species of fungi, but are different stages of 

 the same organism. 



Unfortunately, the presence of this fungus is not apparent at 

 or before planting time. It is particularly noticeable in this 

 country probably during the month of May. It then covers the 

 trunks of young pines of four or five years and over, as well 

 as the trunks and branches of older pine trees, with bright yel- 

 low blisters in which are contained the tecidiospores. These 

 secidiospores appear as a dark yellow powder and cannot ger- 

 minate unless they fall on the leaves of currants or gooseberries 

 (Eibes). On these leaves, however, they develop, send germ 

 tubes into the leaf tissue, and there form a heavy matting of 

 mycelium. Along about the middle of June there are formed 

 on the under side of the leaves of these Ribes plants bright 

 yellow deposits (uredospores) which spread the disease from 

 leaf to leaf on these plants. These uredospores continue to 

 spread throughout the Ribes during the entire season in which 

 young leaves are formed. In the summer, too, still another 

 reproduction cell is found in the shape of yellow-brown strings 

 or sacs, of about the thickness of a hair, on the under side of the 

 leaves of the Ribes bushes, and these are known as teleuto- 



