WHITE-PTN^E BLISTER RUST. 39 



In April, 1918, Dosdall tested in distilled water (in hanging-drop 

 cultures) the viability of aeciospores produced in 1917 (29). On 

 April 19, 1918, a dead white-pine branch bearing a canker which 

 had fruited in 1917 was collected at Rush Lake, Minn. While new 

 aecia were just beginning to break open on other cankers at this 

 time, the spores tested were not new" ones, as they were dug from the 

 bottoms of 1917 cavities after scraping off the outer exposed spores. 

 Nor could there have been new secia pushing up beneath the old 

 ones, as the branch was dead. It was found that from 1 to 2 per 

 cent of the spores germinated in distilled water, each spore producing 

 from 3 to 5 germ tubes. It is barely possible that these spores 

 were from an abnormally late aeciumi (179) and therefore were not so 

 old as Dosdall supposed them to be. Even so, they must have been 

 approximately 6 months old. 



This experiment of Dosdall has been repeated. A dead branch 

 bearing secia of 1918 was collected at Kittery Point, Me., on Febru- 

 ary 25, 1919, and taken to Washington, D. C. Taylor tested the 

 seciospores by hanging-drop cultures in tap water, but no germina- 

 tion of the spores could be demonstrated. Spores of other fungi 

 were present and did germinate. 



York -^ collected a specimen of diseased white pine bearing newly 

 formed secia on April 30, 1918. This was put in a paper bag and left 

 in the laboratory away from direct sunlight until October 5, 1918. 

 He then broke open a still unbroken aecium which had not pushed 

 through the outer bark and made cultures of the spores. He got 

 some germination in tap water under these condition 157 days after 

 collection of the material. The spores were still yellow when the 

 test was made. Spores from recia which had broken open did not 

 germinate. 



During the season of 1918, Pemiington -^ found that in the Adiron- 

 dacks the seciospores remained viable for at least four weeks after 

 being removed from the secia and stored in a dry place. The same 

 season, York found that in the White Mountains a?ciospores from 

 blisters in cankers cut from the tree and kept in the shade out of 

 doors remained viable for 75 days, as shown by tap-water cultures 

 and inoculations on Ribes leaves. 



In 1919, Pennington 2^ found that seciospores, whether brought 

 into the laboratory or left in the field soon lost their viability, less 

 than 1 in 400 germinating after three weeks from the breaking open 

 of the secium producing them. Tests upon the viability of seciospores 

 after they had been exposed to direct sunlight showed a decrease of 

 50 to 75 per cent in viability after three hours' exposure. After 

 an exposure of eight hours, some of the seciospores (1 m 1,500 or 

 2,000) were still viable. 



soYork, H. H. Op.clt. 



SI Pennington, L. H. . Op. eit. 



