240 Retort of the Department of Botany of the 



Experiment No. 4- — On April 10 four more plants were inoculated 

 as in experiments Nos. 1 and 2. 



Experiment No. 5. — On April 10 four potted plants were placed 

 in a large glass inoculation-chamber and their leaves smeared with 

 currant-leaf mush as in previous experiments. The air in the chamber 

 was kept almost constantly at the point of saturation. Drops of 

 water appeared on the margins of the leaves as in the bell- jar experi- 

 ments. On April 16 these plants were reinoculated and kept moist 

 for three days longer. 



Up to May 7 no sign of Cronartium had appeared on any of the 

 plants in the above experiments. 



ORIGIN OF THE OUTBREAKS DISCOVERED. 



All of the experiments having given negative results the origin 

 of the outbreaks of currant rust became more obscure than ever. 

 There seemed now to be but one thing to do, viz., to continue the 

 search for affected pine trees. Early in May, 1913, the State nursery 

 inspectors set out to examine every white pine tree in the vicinity 

 of Geneva. On May 15, one of them, Mr. John Manejr, reported 

 that on the day previous he had discovered two white pine trees 

 affected with blister-rust. Subsequently, his identification of the 

 disease was fully verified. The affected trees were 9 or 10 feet high 

 and about 15 years old. They were in a nursery about one mile 

 west and one-half mile north of the Experiment Station. One of 

 the trees (No. 1) was fairly vigorous and appeared not very much 

 injured by the disease. It was attacked only on the trunk near the 

 ground. A portion of the trunk, extending from the surface of the 

 soil to a height of about seven inches, was thickly covered over 

 about two-thirds of its circumference with conspicuous yellow aecia 

 of Peridermium strobi. The trunk at this point was but slightly, 

 if at all, enlarged. 



Tree No. 2 stood about 120 feet from Tree No. 1. It was bushy 

 and much distorted. Over a portion of the tree the needles were 

 much browned. About 16 inches above the ground the trunk divided 

 into three branches. Here was the seat of the trouble. Aecia were 

 abundant on all of the branches and on the main trunk just below 

 the crotch. A crotch canker had formed and borers were working 

 in the diseased wood. 



