10^^ A ACADEMY OF SCIENCES 
91 
following statements concerning: “The Spruce Rust, Peridermium 
aMetinum Fries, of Europe, is very common, in the form called by 
Peck var. decolorans, on the dwarf Spruces which inhabit the sub- 
alpine summits of the mountains of the northeastern states, and its 
cluster-cups are so abundant toward the end of August in many places 
thac those who walk through the dense dwarf Spruce forests are covered 
with their orange-colored spores. Peridermium aMetinum, Fries, is con- 
sidered in Europe to be connected with Ghrysomyxa rhododendri, DC. 
but in northern Europe it has been supposed to be connected with Ghryso- 
myxa ledi, Albertini & Schweinitz. In northern New Hampshire the 
Peridermium on Spruce, judging by its range and habit, is probably 
connected with Ghrysomyxa ledi, Albertini & Schweinitz, on Ledum lati- 
folium, as no Ghrysomyxa has been found on Rhodendron lapponicum in 
that region.” 
Dr. Farlow^ says, “In short it can be said of our Peridermium hal- 
sameum that it closely resembles in most respects the aecidial form 
of Galyptospora goeppertiana of Europe, and that not only in the White 
mountains but also in other parts of the country there seems to be a 
parallelism between the distribution of the Peridermium and the Galyp- 
tospora.” 
Geographical Distribution. The species of the genus are coet- 
aneous with the distribution of the conifers. an:l t:ic majority occur in 
the northern hemisphere. Of the unconnected species the following are 
credited to America. P. piriforme, P. cerebrum, P. filamentosum, P. 
harknessi, P. raveneli, P. deformans, P. peekii, P. balsameum, P. ephc- 
drae, P. conorum, P. elatinum. 
The following facts are stated in Sargent’s Silva: “The determina- 
tion of the Rusts which infest the conifers is difficult, owing to the 
fact that the greater part of them are aecidia or cluster-cups, 
which resemble one another closely, but, according to recent writ- 
ers, are genetically connected with teleutosporic fungi of quite different 
species. The rusts of Pines, with few exceptions belong to the genus 
Peridermium which, like other aecidia, consist of orange or rust-colored 
spores arranged in chains contained within an envelope composed of 
colorless cells. The old species, Peridermium pini, Reveille, was sup- 
posed to have two forms, one producing cups on the leaves and the other 
cups or irregular disks on the trunks and branches. It has been shown 
that the forms on bark are connected with species of Cronartium, but the 
leaf Peridermium of European Pines is now separated into several species 
connected with different species of Coleosporium which grow on different 
Compositae, as Senecio, Tussilago, Inula, and on Euphrasia and other 
plants. Few experiments have been made with artificial cultures of the 
North American Peridermia, and the determination of our species must 
still be regarded as provisional. Peridermium stroM, common in Europe 
on Pinus strobus introduced from North America, is not known to occur 
in this country, nor has Gronartium ribicolum, Dietrich, with which it 
1. Appalachia 3 : 242. 
2. Silva. 11: 12. 12: 26. 
