242 
Mycologia 
necessary to change the names on 29 packets. Out of the 52 
packets on which the species of the host had not been given, Dr. 
Holm was able to supply 34 determinations. 
Altogether Dr. Holm examined 1050 packets now being used 
for the systematic work under the genus Dicaeoma, and 56 
packets for that previously used under Nigredo, or a total of 
1106. For this important and authoritative assistance in trying 
to render the North American Flor.\ as accurate as possible the 
writer desires to publicly extend to Dr. Holm most hearty thanks. 
In the preliminary manuscript for the next rust number of the 
North American Flora at the present writing (February i, 1913) 
there are recognized 24 species of Dicaeoma occurring upon 106 
species of Carex. These 24 species are represented by 1200 
North American collections, 150 collections having been added 
since the material was returned by Dr. Holm in November last. 
Although this seems like a vast array of material for the rusts 
on a single genus of hosts, yet one half of the 24 species are 
represented by 13 or less collections each, and four by only one 
or two collections each, these four species being from readily ac- 
cessible localities in Delaware, West Virginia, Wisconsin and 
South Dakota, except one which is from Guatemala. Some 
stress should be laid upon this situation as indicating the desira- 
bility that collectors search for Carex rusts more assiduously, 
especially for such as appear to be associated in the field with 
definite heteroecious aecia, and not follow the practice of a 
famous mycologist of a prominent university who once confessed 
that he usually threw away Carex rusts — they were so trouble- 
some to name. 
It is to be hoped that no one will be discouraged by the fact 
that the chances are not many for picking up one of these rarer 
species, taking the comparative number of collections under each 
species as an indication. The three most commonly collected spe- 
cies are one with aecia on Aster, Solidago, Erigeron and similar 
genera, now passing under several names, which is represented 
by 208 collections, one with aecia on I/rtica represented by 152 col- 
lections, and one with aecia on Ribes represented by 146 collec- 
tions. The remaining seven large species range from 86 to 18 
collections each. 
