328 
J. C. ARTHUR 
be remembered that much of the northern part of Guatemala yet re- 
mains to be explored, especially the great department of Peten which 
includes nearly one third of the area of the country and is botanically 
a veritable terra incognita. Even the better known parts will yield 
many more species, especially the cool summits of the high mountains. 
As Professor Holway wrote in May, 191 7, "the Volcan de Santa Maria 
is very rich and has only been scratched;" and the same might be said 
of other localities in this enumeration, even those most frequently 
mentioned. 
The author has been assisted in the study of the Guatemalan ma- 
terial not only by Professor Holway, but also by various members of 
the botanical staff of the Purdue University Agricultural Experiment 
Station, working in connection with the preparation of the rust portion 
of the North American Flora, to whom many thanks are due, and 
especially to Professor H. S. Jackson and Dr. E. B. Mains, who have 
described some of the species. 
In order to bring out more clearly the several groups of rusts, their 
relationships, and the association of the new species, the list of species 
will be presented in several parts. The first part includes twenty-two 
species belonging to the families Coleosporiaceae and Uredinaceae. 
This group is more notable for its familiar names than for novelties. 
The heteroecious species, Coleosporium Ipomoeae, C. Viburni, Melamp- 
sora Bigelowii, M. arctica, Cronartium Quercus and C. coleosporioides, 
common in the northern United States, seem to be abundant in this 
tropical country. It should be noted, however, that with the excep- 
tion of the last-named only uredinia are recorded. Pines are common 
enough in the region, especially at higher altitudes, but little search 
has yet been made for aecia (Peridermiums) on them at the season of 
the year when they are most likely to be found. The aecia possibly 
may be rare or wanting for these species so far south, unless Cronartium 
coleosporioides, which shows telia, is an exception. New hosts are 
recorded for this last species. 
Finding the common grape-vine rust of warmer regions on a native 
species may prove to be a matter of economic importance. Although 
first reported from America, the principal observations regarding the 
nature of the rust have been made in India and Japan. 
