UREDINALES ON CAREX IN NORTH 
AMERICA 
J. C. Arthur 
In the systematic work on Uredinales in the North American 
Flora, a monographic treatise, every entry is based upon a col- 
lection in the author’s herbarium, either an original one, or some 
data to represent a collection in another herbarium. Whatever 
advantage in fundamental accuracy is secured in this work prob- 
ably depends largely upon the application of four tests which are 
the foremost guides used in systematically placing every collec- 
tion : ( I ) life cycle, so far as direct or collateral evidence can be 
found; (2) name and systematic position of host; (3) micro- 
scopic characters of sorus and spores; (4) the limitation of a 
species in view of the influence of host and possible occurrence of 
races. 
It has not been many years since most collections of Carex 
rusts were largely labelled “ Puccinia Caricis” or “P. caricina’’ 
and said to be on “ some species of sedge,” or on ^ Carex sp.,” 
and with such material the work on the North American Flora 
began. 
As to the first test to be applied to each collection, regarding 
the life cycle, Carex rusts may be assumed to be uniform in hav- 
ing their spore forms of the general character of those of Puc- 
cinia graminis and in being heteroecious. 
As to the second test, regarding the host, slow but steadily in- 
creasing progress has been made in securing authentic 'determina- 
tion of the hosts. All Carex rusts belong either to the genus 
Nigredo (having i-celled teliospores) or Dicaeoma (having 
2-celled teliospores). The material for the species under Ni- 
gredo, published about a year ago, consisted of 21 collections with 
leaves and stems only, and 35 other collections accompanied by 
more or less perfect fruiting parts. The determinations of the 
latter had been verified or completed by comparison with the 
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