1918] JACKSON—PUCCINIA 291 
and Costa Rica was loaned to the writer for study by Dr. 
J. C. AntHUR, to whom the material was sent. Professor HoLwAy 
has also kindly furnished other material from his very extensive 
herbarium. A number of collections made by the late 
W. A. KELLERMAN in Guatemala have also been included in this 
study. Most of the type collections of previously described 
species have been examined. A few from South America and 
Africa have not been seen, as the original specimens are in European 
herbaria and on account of the present unsettled conditions are 
not available. 
The writer is under great obligations to Dr. J. C. ARTHUR and to 
Professor E: W. D. Hotway for the loan of material at their disposal 
and for reading the manuscript of this paper. Acknowledgment is 
also gratefully made to the members of the staff of the botanical 
department of the Purdue University Experiment Station for 
assistance in the details of the work. The species described as new 
from Guatemala and Costa Rica are published jointly under the 
authorship of Professor Hotwavy and the writer. The descriptions 
and notes, however, were prepared entirely by the writer, and he 
assumes all responsibility for any errors which future investigations 
may bring to light. 
KEY TO SPECIES 
Teliospores smooth or appearing so, often i te rugose 
Teliospores colorless or light cinnamon brown, smooth 
Teliospores uniformly thick, rarely slightly chicken above 
Teliospores averaging more than 6oy in lengt 
Aecia present in oa history 
Peridium prese 
Teliospores ma pin width; urediniospores 19-22 by Sart 
. Teliospores 18-20 in width; urediniospores a ta De ewes 
PVs siwGueeyy Coe elute les Uber ere 2. P. membranacea 
Peridium wanting; urediniospores 23-28 by 29-34. 3. P. erratica 
Aecia lacking in life history or unknown 
O, I, III present; teliospores 16-24 by 56-80pn.. 4. P. Arthuriana 
III only described; spores 20-27 by 45-70p.... 5. P. vernoniicola 
Teliospores averaging less than 60 in length 
Teliospores less than gon long.............- 6. P. Vernoniae-mollis 
Teliospores more than 40 long 
Occurring on Vernonia 
