Arthur and Fromme: Value of Pore Characters 33 
The equatorial-pored condition is most common here and is 
present in 25 species, while eleven species have superequatorial 
pores and three have subeqnatorial pores. 
The practical importance of a thorough understanding of the 
pore characters of the urediniospores of the grass and sedge rusts, 
apart from the possible clues of relationship and phylogeny that 
may be derived from it, lies in the application of the knowledge to 
the identification of incomplete material. In many cases collec- 
tions that are of considerable importance in mapping the range 
of a species or in determining its validity are represented by a few 
fragments of leaves that the taxonomist is unable to place and the 
rust material may be scanty and wholly or chiefly in the uredinial 
stage. The too common practice of gathering a few infected 
leaves without infloresence or fruit supplemented by the failure 
to properly label the collection in the field leads to many errors 
in the naming of hosts which the uredinologist is sometimes able 
to rectify through the proper identification of the parasite. If 
a rust in question on an unidentified grass-like fragment of leaf 
has scattered uredinio.spore-pores or a greater number than five 
the assumption is that the host is a grass since but a single sedge 
rust has scattered pores and none has more than five. If the pores 
are superequatorial, the host is most certainly a sedge. 
With the few broad bases of separation afforded by the pore 
characters and with the other supplementary characters of the 
urediniospores, it is often possible to determine the species of rust 
from urediniosporic material alone, which is a far cry from the 
situation prevailing not many years ago when grass and sedge 
rusts, especially the latter, were considered the most difficult of 
all the rusts to determine, and utterly hopeless when only uredin- 
iospores were present. 
Purdue University, 
Lafayette, Indiana. 
