Arthur and Kern: North American Peridermium 111 
sylvestris, is mentioned. The occasion of the citation was the 
appearance of the alternate stage on Senecio vulgaris in Rhode 
Island. But the rust did not become established, and has not been 
reported since. The aecial form has never been seen in this 
country. 
The three main sources of information which have led to a 
better understanding of the forms of Peridermium on pine are 
increased collections with field observations, culture work, and 
microscopic comparison. 
The collections in herbaria are remarkably few and imper- 
fect, due doubtless to two main reasons. These forms of rust ap- 
pear early in the season when not many collectors of rusts are in 
the field, and consequently even when abundant they are only 
incidentally represented in sets of specimens. The bark forms 
for the most part produce large galls, sometimes a foot or more in 
diameter, and almost invariably cumbrous and troublesome in 
comparison with most rust specimens. In consequence only a 
small fragment of the original gall as a rule is taken, and often 
with scant data. Specimens in the best condition to study must 
generally be placed in boxes, as fruits and woody fungi are, 
rather than in mycological packets. Field observations relative 
to the probable alternate forms are meagre and principally by a 
few observers in recent years. 
Culture work is not so simple and expeditious as with most 
other groups of rusts. The information obtained in this way is 
invaluable, and it will never be possible to have definite knowl- 
edge of the species until many more cultures are made, than are 
at present available. Up to the present writing the following is 
the record of cultures made in North America with the several 
forms of Peridermium on pine, both foliicolous and caulicolous. 
Cultures in the field may result in valuable information, and 
can afterward be substantiated under glass, if necessary. Damp 
cool weather is most favorable for the work. Sowings from 
teliosporic material of Coleosporium may be made by suspending 
fresh material over growing pines, more conveniently over low or 
seedling pines, care being taken that such material does not wilt 
for some hours, and that the pine leaves have a moist surface, at 
least during one night. In the case of Cronartium the germinat- 
