330 
JAMES R. WEIR AND ERNEST E. HUBERT 
of the fir must become infected during the same summer or fall in 
which the telia mature on the fern. Such being the case the advent 
of lower temperatures prevents the fruiting on the needles until 
favorable conditions are again present, which is in the early spring of the 
following year. This is borne out by the collection of the aecial stage 
fully matured on Abies grandis as early as April 12, 19 16. This is the 
earliest collection of any needle rust made in this locality. Other 
collections were made on April 14, May 2, and June 17, of the same 
year. 
On June 19, 1916, sowings of aeciospores of the above fungus on 
Abies grandis were made on two plants of Pteridium aquilinum pu- 
bescens. The plants were raised in the greenhouse at Missoula, Mont., 
from rhizomes dug up in the field on September 4, 1915, and the inocu- 
lations were made by the use of celluloid cylinders and cotton plugs. 
On July 25, 1916, a medium infection of uredinia was found on one of 
the plants while the other bore no results. The control plants re- 
mained normal. A large number (15) of collections of the fungus on 
Pteridium aquilinum pubescens (fig. 2) made throughout Idaho, 
Washington, and Oregon was always in immediate association with 
the rust on the needles of Abies. In one particular instance at Lucern 
Lake, Wash., August 23, 19 16, a lake flat was grown up to young 
Abies grandis and the braken fern. The foliage of the latter was 
completely parasitized by Uredinopsis pteridis D. & H. while the 
needles of the fir were seriously infected with the aecial form of the 
fungus. No other forest tree rust was present in the vicinity. After 
a close comparison of the microscopical characters of the above 
produced uredinial stage with authentic material of Uredinopsis 
mirabilis, U. osmundae, U. struthiopteridis, U. atkinsonii, U. phegop- 
teridis, and U. pteridis, it was found to coincide with the latter. A 
careful study of the published descriptions^ of the species of Uredinopsis 
in connection with the above culture showed that no great differences 
existed between U. copelandi Sydow and U. pteridis other than the 
hosts. A slight difference in the size of the spores is to be noted. 
U. pteridis has a spore measurement of 11-18 by 30-58 ix and that of 
U. copelandi is 14-18 by 31-40 /x, a difference in length of about 19 /x. 
This variation is no greater than is found usually occurring in spores 
of a single species. In comparing the five species of Uredinopsis 
which have been found to produce an identical aecial stage on Abies 
^ Arthur, J. C. Uredinales. N. Amer. Flora 7: 115. 1907. 
