580 Artuur: NEW SPECIES OF UREDINEAE 
Aecidium libertum sp. nov. 
O. Pycnia not seen. 
I. Aecia hypophyllous, evenly distributed over the whole sur- 
face of the leaf, substratum neither thickened nor discolored; 
peridium short-cylindrical, 0.3—-0.4 mm. in diameter, margin some- 
what recurved, lacerate, peridial cells cuboidal, squarely abutted 
except a downwardly imbricated outer tooth, outer wall smooth, 
5-7u, inner wall slightly thinner, 3-4u, and closely verrucose; 
aeciospores angularly globoid, 17-19 by 18-23; wall pale yellow, 
thin, Iu, closely and finely verrucose. 
On Urtica chamaedryoides Pursh, Sapulpa, Indian Territory 
(now state of Oklahoma), May 1, 1895, B. F. Bush 1269, com- 
municated by A. G. Johnson, who found the material in the 
phanerogamic herbarium of the Missouri Botanical Garden, St. 
Louis, Mo. This form is strikingly different from the aecia com- 
monly found on Uriica, which belong to the cosmopolitan Carex 
rust, Puccinia Caricis, only in the distribution of the aecial sori 
over the host. In the structure of the aecium, and in the size, 
shape, and markings of the peridial cells and aeciospores, the two 
forms are essentially alike. Although the mycelium occupies all 
or most of each leaf, and most of the leaves on the plant, yet it 
may not be a perennial mycelium, but be diffused from an early 
spring infection. Most of the rusts having evenly scattered aecia, 
especially if the mycelium is annual, are autoecious, and there is 
considerable probability that in this case the associated telia will 
be found to follow upon the same host, and without the accompani- 
ment of uredinia. In this connection it may be pointed out as 
of incidental interest that the teliospores of the leptoform, Puccinia 
Urticae Barclay, found in India, agree essentially with the telio- 
spores of Puccinia Caricis (Schum.) Schrét. (P. Urticae Lagerh.), 
adding another example of the curious morphological agreement 
between heteroecious species with many spore-forms and auto- 
ecious species with one spore-form affecting the same host, pointed 
out by Dr. Tranzschel of St. Petersburg. The new Aecidium 
on Urtica, here described, may prove to be an extension of this 
same example. 
PuRDUE UNIVERSITY, 
LAFAYETTE, INDIANA. 
