78 BOTANICAL GAZETTE [ AUGUST 
apparent discrepancy between the two species previously 
studied. The selection of A. Tragopogonis has proved particu- 
larly fortunate, for it has led directly to a solution of the prob- 
lem. The conditions in this species, while to a certain extent 
similar to those described for A. candida, made evident the 
necessity of a critical reexamination of the latter. I have 
included A. candida, therefore, in this investigation. 
The material of A. Portulacae on Portulaca oleracea, and A. 
Tragopogonis on cultivated Zragopogon and Ambrosia artemisae- 
folia, was collected at Syracuse, New York. The material of A. 
candida on Bursa was collected at Columbus, Ohio. All the 
material'was fixed in chrom-acetic killing fluid and imbedded in 
paraffin in the usual way. The methods in general were the 
same as those employed in the study of A. Blitz, and are 
described in detail in Bor. Gaz. 28: 233. 1899. The Flemming 
triple stain was used throughout, and I am convinced that it is 
best for the study of Albugo, although it is exceedingly sensi- 
tive to manipulation, and the different species of Albugo require 
quite different treatment. 
The results of this investigation are presented in three sec- 
tions, entitled “descriptive,” ‘ phylogeny,” and ‘general consid- 
erations.’ The first section describes the phenomena observed, 
avoiding theoretical considerations and presenting only what may 
be regarded as established facts. The second section considers 
the phylogenetic bearing of this research. The third section 
considers the genus from the comparative standpoint, an attempt 
being made to interpret the significance of the phenomena, and 
to call attention to anaiogous phenomena in other organisms. 
The species discussed were kindly determined by Dr. Paul 
Magnus, who assures me that the names and synonymy are as 
follows: Atsuco PortuLacar (DC.) O. Ktz. (Uredo Portulacae 
DC., Cystopus Portulacae Lév.); A. Tracopoconis ( Pers.) S. F. 
Gray (Uredo candidus Tragopogonis Pers., Cystopus Tragopogonts 
Schrot., Uredo Tragopogonis DC., Cystopus cubicus Lév., C. spinu- 
losus DBy., Uredo cubica Strauss); A. CANDIDA ( Pers.) O. Ktz. 
( Uredo candidus Pers.). 
