UREDINALES OF PORTO RICO BASED ON 
COLLECTIONS BY F. L. STEVENS 
J. C. Arthur 
The material illustrating the rust flora of Porto Rico, which 
was collected by Dr. F. L. Stevens and placed in my hands for 
study, represents a specially valuable contribution to the knowl- 
edge of tropical fungi. There were 650 numbers of the ma- 
terial submitted, which were mostly collected during the year 
1913, only some twenty-three having been secured during the 
year 1912 and seven during January, 1914. 
This is an especially notable achievement, as all other collec- 
tions of rusts from the island taken together only slightly exceed 
100. These range mostly through the last sixteen years. 
Among the previous collectors the two having the greatest knowl- 
edge of the Uredinales are Prof. E. W. D. Holway, leading with 
25 collections made in January and February, 1911, and Dr. G. 
P. Clinton, following with 21 collections made in April, 1904. 
Some rusts have been included in collections made during the 
last few years by the botanists at the Experiment Station of the 
Porto Rico Sugar Growers’ Association, about twenty-five of 
which have come to my attention. 
Until the Stevens’ material was available the general impres- 
sion of the rust flora of Porto Rico has been that it was scanty 
and lacking in interest. Professor Holway, who is famous as a 
collector of microfungi, wrote from San Juan on January 29, 
1911 : “ I have just come in from our trip across and around the 
island ; rusts are very scarce.” Again in a letter from Min- 
neapolis, Minn., dated March 21, 1911, he writes; “I am just 
home from Porto Rico ; I will send you the specimens soon. 
There are not many, but more than Sintenis got in his three 
years there.” It now appears from the work of Dr. Stevens, 
however, that there are plenty of species in the island and some 
of exceptional interest, although the rust flora is not generally 
as conspicuous as is usual in temperate regions. 
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