Fraser: Further Cultures of Heteroecious Rusts 235 
Uredinia of Uredinopsis Stnithiopferidis appeared on Onoclea 
Struthiopteris in abundance on June 6. The spores were oozing 
out on June 8. The other ferns remained free from infection. 
Another sowing of a collection also believed from field observa- 
tion to be connected with Uredinopsis Struthiopteridis was made 
on Onoclea Struthiopteris and Phegopteris Dryopteris on June 29, 
with uredinia rather abundant on July 8 on the former and no 
infection on the latter. A third sowing of a collection similar to 
the others on Onoclea Struthiopteris and Osmunda Claytoniana 
on July 2 produced very abundant infection on Onoclea Stric- 
thiopteris, the uredinia appearing on July 8. Teliospores were 
present on July 30. Osmunda Claytoniana was not infected. 
Five pots of Onoclea Struthiopteris obtained at the same place 
and at the same time as those used in the experiments were kept 
as checks and remained entirely free from infection. 
The place where the aeciosporic material was collected was 
kept under observation, and about a fortnight after the spores of 
Peridermium balsameum were being shed, the ferns of Onoclea 
Struthiopteris which grew immediately beside showed the ure- 
dinia of the rust in abundance. The distribution of the ure- 
dinia was such that it indicated the Peridermium on Abies as 
the source of infection. 
Uredinopsis Osmundae Magn. 
Teliosporic material of this rust on Osmunda Claytoniana L. 
was placed in a moist chamber, and the teliospores germinated 
freely in a few days. The leaves bearing the germinating telia 
were then suspended above plants of Abies balsamea on May 26. 
Pycnia were observed on June 10, and aecia on June 18. Five 
more sowings were made and in all cases the pycnia and aecia of 
Peridermium balsameum followed. In several cases the ger- 
minating teliosporic material was placed immediately above the 
young shoots of Abies and these showed marked infection, while 
the other shoots remained practically free. 
Observations in the field strengthened the results of the cul- 
tures. Whenever the writer found a very abundant development 
of the uredinia of this rust on Osmunda in early summer it was 
beneath, or close by, trees of Abies balsamea that showed a rich 
