310 
Mycologia 
Peridermium ribicola 
0. Pycnia amphigenous, scattered, sparse, low, conoidal, sub- 
corticular, noticeable, dehiscent by a longitudinal slit, chestnut- 
brown, 0.5-1 mm. long by 0.3-0.5 mm. broad, about 100 ju, tall. 
1. Aecia from a limited mycelium, amphigenous, one to several 
on each leaf, not forming spots on leaves, erumpent from a nar- 
row slit, flattened laterally, 0.5 to i mm. long by 0.5 to 0.8 mm. 
high ; peridium colorless, fragile, cells slightly or not at all over- 
lapping, outer walls smooth to slightly granular, inner moderately 
verruculose, lower peridial cells elliptical, lanceolate or oval, 
33-50 by 16-24 ;ii, walls 2-3 /x thick, upper peridial cells approxi- 
mately isodiametric, irregularly orbicular, 18-30/x across, walls 
2-4 /X thick; aeciospores elliptical-oblong, oval or obovate, 20-28 
X 30-43 /X, average size for ten spores 23.7 X 36.2 /x ; walls color- 
less, 2-3 jx thick, verrucose, with rather coarse irregular warts, 
which are tardily deciduous, without a smooth area on spore 
walls. 
Both collections of Peridermium ribicola were made at an ele- 
vation of about 7,500 feet near the upper limit of the range of 
pihon in these two canyons (Bear and Tejano). Snow was still 
on the ground in the upper portion of the canyons and the ground 
was still frozen on some of the more protected slopes in the im- 
mediate vicinity of the infected pinons. The season was so early 
that a snow storm occurred while the writer was collecting the 
rust. Both collections had already discharged most of their 
spores. The above facts indicate that the peridia of this Perider- 
mium were probably well developed before all of the snow had 
disappeared from under the pinons. 
No indications of the aecial stage of this fungus were found 
below 6,500 feet elevation, although the pihon was still abundant. 
The comparatively high altitude (for the aecial host) at which 
this Peridermium occurs and its very early appearance in the 
spring will probably explain why it has not been discovered 
before. 
The coleosporial stage occurs at much lower elevations than 
the aecial since the writer found the rust on Ribes plants in Albu- 
querque (4,950 feet elevation). The coleosporial stage evidently 
reaches these lower altitudes through the successive infection of 
the Ribes plants throughout the summer months by the uredinio- 
spores, thereby materially extending the range of the rust beyond 
that of its aecial stage. 
