Sept, a, x9x£ 
Pinon Blister-Rust 
423 
the plants, but none have been found killed from the effects of the fungus. 
On leaves attacked by the fungus the uredinia and telia cause a char¬ 
acteristic spotting. The spots vary in color from a light yellow-green 
before frost occurs to a purplish brown afterwards. This spotting is 
most pronounced on leaves of R. aureum and R. odoratum. 
SUMMARY 
The species of Cronartium native on Ribe s spp. and Grossularia spp. 
in Colorado and Arizona is described for the first time and named “Cro¬ 
nartium occidentale” 
The aerial stage of this fungus is proved to be a form of Peridermium 
on the pinons, or nut pines, Pinus edulis and P. monophylla , and is now 
given the form-name “Peridermium occidentale ” 
Cronartium occidentale is widespread throughout the pinon region of 
Colorado, extending into Arizona. Further surveys will no doubt 
greatly extend the known range of the species. 
The common native host for the telial stage of this fungus is Ribes 
aureum , although it occurs occasionally on R. odoratum , R. inebrians, 
and Grossularia leptantha. 
Cronartium occidentale has been successfully inoculated on Ribes 
americanum, R. aureum, R. coloradense , R. giraldi , R. malvaceum, R. 
nigrum , R. glandulosum , R. sanguineum , Ribes sp., Grossularia inermis , 
G . missouriensis , and G. reclinata X G. hirtella. 
Peridermium occidentale , so far as known, attacks ony the pinon 
pines. Inoculations have been made on 23 species of pines to ascertain 
whether it will attack other kinds of pines. 
Cronartium occidentale differs essentially from C. ribicola, cause of the 
white-pine blister-rust, especially in the aerial stage. A synopsis of 
these variations is given. 
Cronartium occidentale is apparently able to overwinter and maintain 
itself independent of the aecial stage. Only circumstantial evidence in 
support of this view has been obtained. 
LITERATURE CITED 
(1) Arthur, J. C. ‘ 
1907. UrEdinalES ... In North American Flora, v. 7, pt. 2, p. 85-160. 
Cronartium ribicola, p. 122-123. 
(2) -and Kern, F. D. 
1914. north American species op peridermium on pine. In Mycologia, V. 6, 
no. 3, p. 109-138. 
(3) Colley, R. H. 
1917. DIAGNOSING WHITE-PINE BLISTER-RUST FROM ITS MYCELIUM. In Jour. Agr. 
Research, v. 11, no. 6, p. 281-286, x fig., pi. 31. 
(4) Hedgcock, G. G., and Long, W. H. 
1915. A DISEASE OP PINES CAUSED BY CRONARTIUM PYRIFORME. U. S. Dept. 
Agr. Bui. 247, 20 p., I fig., 2 pi. Literature cited, p. 20. 
