Arthur and Kern : North American Peridermium 133 
In several instances our attention has been called to the damage 
which this species is doing to seedlings of the Scotch pine in 
nurseries. The general similarity in appearance and habit has led 
some observers to suggest that perhaps the Scotch pine and white 
pine blister rusts might be the same species. In this connection 
the morphological differences above pointed out are of interest, 
but of still greater importance is the fact that Clinton has suc- 
ceeded in culturing the Scotch pine rust on Comptonia aspleni- 
folia. The relationship of the pitch pine specimens here listed to 
Cronartium Cornptoniae is also unquestionable. With the data 
obtained from field observations, morphological characters, and 
infection experiments it seems that we are safe in concluding that 
the pitch and Scotch pine rusts are the same species and quite dis- 
tinct from the white pine species. 
More recently (June, 1913), specimens have come to hand 
showing that this species is also causing damage to Pinus pon- 
derosa in a nursery in northern Wisconsin. Since the Cronartium 
on Comptonia has been collected in the same region the outbreak 
may be explained. With the exception of this locality and one in 
the fruticetum of the Missouri Botanical Garden, where an in- 
fected tree was doubtless planted, the species seems to be pretty 
well confined to the eastern United States. 
Recently (Phytopath. 3: 308. Dec. 1913) Spaulding has given 
an account of the injury which this species of rust has been ob- 
served to do among cultivated pines. 
16. Peridermium cerebrum Peck, Bull. Buffalo Soc. Nat. Sci. 
1 : 68. 1873 
Peridermium Harknessii Moore, Bull. Calif. Acad. Sci. 1 : 37. 
1884. 
Aecidium deformans Mayr, Waldungen Nordam. 119. 1890. 
Aecidium giganteum Mayr, Waldungen Nordam. 120. 1890. — 
Bot. Centr. 58 : 149. i8od. 
Peridermium deformans Tubeuf, Pflanzenkr. 429. 1895. 
Peridermium giganteum Tubeuf, Pflanzenkr. 429. 1895. 
Aecidium cerebrum Dietel, in Engler & Prantl, Pflanzenfam. i 1 **: 
79. 1897. 
Aecidium Harknessii Dietel, in Engler & Prantl, Pflanzenfam. 
i 1 **: 79. 1897. 
