164 
PROCEEDINGS OF SOCIETIES. 
discovered it on the 26th of May last. On the 20th inst. I again 
visited the locality for the purpose of noting the changes which had 
occurred during the interval. The fungus belongs to the genus 
Peridermium, order ^cidacie, and appears both on the limbs and 
trunks of young trees of the variety Pinus ponderosa, generally 
forming a complete circle around the tree, its sporidia appearing as a 
zone of bright orange yellow. 
The spores first germinate beneath the cuticle, which it destroys. 
Owing to the irritation of this presence, an abnormal thickness of the 
cambium is produced, which, in turn, gives place to an excessive 
growth of woody fibre. 
This process being repeated from time to time, a large bulbous 
expansion is soon formed, so that as often occurs a stem of but an 
inch in diameter is enlarged to that of four or five. 
Above this bulb the further development of the stem is retarded 
or arrested altogether, its place being supplied by a dense tuft of 
minute branches. 
As no reference to this fungus is found in any of the books at my 
command, I am inclined to the belief that it is a new variety. 
Yesterday I received a letter from Professor W. G. Furlow, of 
Cambridge, Mass., in which he says : " I send you a specimen of 
Peridermium, which is attacking the Pinus ponderosa of this vicinity. 
Do you find it in California ? " 
As the specimen sent by the Professor agrees in every essential 
particular with the one sent to the Society, it would appear that the 
fungus is attacking the forests in the eastern as well as the western 
portion of the United States. 
But one other variety of Peridermium is yet known upon this 
coast, and that is found upon the foliage of the Pinus insignis, 
growing in the Golden Gate Park, San Francisco, in the month of 
January last. This variety we then identified as the P. pini, which 
so far has not produced any special damage. 
In the vicinity of Colfax, the fungus appears to be limited to an 
area of but a few acres in extent. Within that area, however, it is 
destroying the young growth, and should it become generally 
disseminated, it bids fair to do great harm to the timber trees of this 
coast. 
H. W. Harkness. 
C. Mason Kinne, Esq., 
Secretary San Francisco Microscopical Society. 
A motion by Mr. J. P. Moore, that the fungus be named by the 
Society Peridermium Harknessiif was carried unanimously, after which 
the meeting adjourned. 
