Fraser: Further Cultures of Heteroecious Rusts 237 
Another sowing on Onoclea sensibilis on July 3 also gave 
abundant infection, the uredinia appearing by July 10. Five 
pots of plants from the same place as those used in the experi- 
ments and obtained at the same time were kept as checks and 
showed no infection. 
Observations in the field strengthened the evidence of connec- 
tion furnished by the cultures. It was noticed for several years 
that wherever this rust was common on Onoclea in the following 
spring the firs near were abundantly infected with Pcridermium 
balsameum, but the sequence of spore forms was not carefully 
observed. This season several places, where this rust was known 
to be common on Onoclea sensibilis in 1911, were kept under ob- 
servation. It was found that Periderminni balsameum appeared 
abundantly on the trees of Abies balsamea that grew near about 
June 25. In about ten days uredinia appeared on the ferns of 
Onoclea sensibilis growing immediately beneath, and soon became 
common. 
The experiments and field observations here described seem to 
the writer to establish the connection of the five species of Ure- 
dinopsis used in the experiments with the white-spored aecia on 
Abies balsamea which have passed as Periderminni balsameum. 
The question whether these are distinct species with similar aecia 
or whether they should be included under one species needs fur- 
ther study. It will be noticed that the evidence of cultures, as far 
as it goes, indicates that the species established are good. 
The examination of the cultures and collections of the fern 
rusts of the genus Uredinopsis convinced the writer that the first 
spore form to appear is the urediniospore. The spores which 
have been regarded as aeciospores were rarely present in the col- 
lections and never appeared first. 
In the genus Hyalopsora the aeciospores were found to be the 
first to appear. 
PucciNiASTRUM ]\Iyrtilli (Schum.) Arthur 
Teliosporic material of this rust on the leaves of Vaccinium 
canadense Kalm. was suspended on May 28 above a young tree 
of Tsuga canadensis (L.) Carr. Pycnia were observed on a 
number of leaves on June 10, and aecia began to appear on June 
